After 10 minutes I closed Steam and started a new attempt with Terminal.
Now I got different output and Steam started:
`~ $ steam
Running Steam on solus 4.1 64-bit
STEAM_RUNTIME is disabled by the user
/home/tyros/.local/share/Steam/ubuntu12_32/steam
[2020-11-02 14:54:39] Startup - updater built Apr 4 2020 00:37:13
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
[2020-11-02 14:54:39] uninstalled manifest found in /home/tyros/.local/share/Steam/package/steam_client_ubuntu12 (1).
[2020-11-02 14:54:39] Found pending update
[2020-11-02 14:54:39] Update wird installiert...
Installing breakpad exception handler for appid(steam)/version(1586022601)
[2020-11-02 14:54:40] Paket wird extrahiert...
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
Installing breakpad exception handler for appid(steam)/version(1586022601)
[2020-11-02 14:55:07] Update wird installiert...
[2020-11-02 14:55:08] Bereinigen...
[2020-11-02 14:55:08] Aktualisierung abgeschlossen, Steam wird geladen...
[2020-11-02 14:55:08] Shutdown
Restarting Steam by request...
Running Steam on solus 4.1 64-bit
STEAM_RUNTIME is disabled by the user
Can't find 'steam-runtime-check-requirements', continuing anyway
/home/tyros/.local/share/Steam/ubuntu12_32/steam
[2020-11-02 14:55:10] Startup - updater built Oct 23 2020 20:26:36
/tmp/dumps insufficient permissions - delete and recreate
Installing breakpad exception handler for appid(steam)/version(1603487799)
[2020-11-02 14:55:10] Failed to load cached hosts file (File 'update_hosts_cached.vdf' not found), using defaults
[2020-11-02 14:55:10] Using the following download hosts for Public, Realm steamglobal
[2020-11-02 14:55:10] 1. http://client-download.steampowered.com, /client/, Realm 'steamglobal', weight was 100, source = 'baked in'
[2020-11-02 14:55:10] 2. http://media.steampowered.com, /client/, Realm 'steamglobal', weight was 1, source = 'baked in'
Installing breakpad exception handler for appid(steam)/version(1603487799)
[2020-11-02 14:55:10] Installation wird überprüft...
[2020-11-02 14:55:11] Verification complete
Loaded SDL version 2.0.12-hg-13609:34cc7d3b69d3
Gtk-Message: 14:55:11.279: Failed to load module "canberra-gtk-module"
Installing breakpad exception handler for appid(steam)/version(1603487799)
STEAM_RUNTIME_HEAVY: Disabled
[1102/145511.907268:INFO:crash_reporting.cc(247)] Crash reporting enabled for process: browser
[1102/145511.951430:WARNING:crash_reporting.cc(286)] Failed to set crash key: UserID with value: 0
[1102/145511.951561:WARNING:crash_reporting.cc(286)] Failed to set crash key: BuildID with value: 1603484818
[1102/145511.951574:WARNING:crash_reporting.cc(286)] Failed to set crash key: SteamUniverse with value: Public
[1102/145511.951582:WARNING:crash_reporting.cc(286)] Failed to set crash key: Vendor with value: Valve
[1102/145512.034881:WARNING:crash_reporting.cc(286)] Failed to set crash key: UserID with value: 0
[1102/145512.035167:WARNING:crash_reporting.cc(286)] Failed to set crash key: BuildID with value: 1603484818
[1102/145512.035234:WARNING:crash_reporting.cc(286)] Failed to set crash key: SteamUniverse with value: Public
[1102/145512.035298:WARNING:crash_reporting.cc(286)] Failed to set crash key: Vendor with value: Valve
[1102/145512.036357:INFO:crash_reporting.cc(247)] Crash reporting enabled for process: gpu-process
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Warning: failed to set thread priority: set failed for 8: -1: setpriority() failed
Warning: failed to set thread priority: set failed for priority 8
Warning: support for elevated priorities is most likely unavailable, suppressing future warnings
Installing breakpad exception handler for appid(steam)/version(1603487799)
Warning: failed to set thread priority: set failed for 8: -1: setpriority() failed
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
[1102/145512.291211:ERROR:sandbox_linux.cc(372)] InitializeSandbox() called with multiple threads in process gpu-process.
[1102/145512.363137:WARNING:crash_reporting.cc(286)] Failed to set crash key: UserID with value: 0
[1102/145512.363395:WARNING:crash_reporting.cc(286)] Failed to set crash key: BuildID with value: 1603484818
[1102/145512.363461:WARNING:crash_reporting.cc(286)] Failed to set crash key: SteamUniverse with value: Public
[1102/145512.363523:WARNING:crash_reporting.cc(286)] Failed to set crash key: Vendor with value: Valve
[1102/145512.364600:INFO:crash_reporting.cc(247)] Crash reporting enabled for process: utility
CAppInfoCacheReadFromDiskThread took 423 milliseconds to initialize
CApplicationManagerPopulateThread took 863 milliseconds to initialize (will have waited on CAppInfoCacheReadFromDiskThread)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Proceed to auto login
Opted-in Controller Mask for AppId 0: 0
(steam:2185): Gtk-WARNING **: 14:55:14.022: gtk_disable_setlocale() must be called before gtk_init()
vkEnumeratePhysicalDevices failed, unable to init and enumerate GPUs with Vulkan.
BInit - Unable to initialize Vulkan!
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
BuildCompleteAppOverviewChange: 0
vkEnumeratePhysicalDevices failed, unable to init and enumerate GPUs with Vulkan.
BInit - Unable to initialize Vulkan!
Installing breakpad exception handler for appid(steam)/version(1603487799)
roaming config store loaded successfully - 8144 bytes.
migrating temporary roaming config store
BRefreshApplicationsInLibrary 1: 73ms
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
[1102/145522.785676:INFO:crash_reporting.cc(270)] Crash reporting enabled for process: renderer
Installing breakpad exception handler for appid(steam)/version(1603487799)
[1102/145523.613627:INFO:crash_reporting.cc(270)] Crash reporting enabled for process: renderer
Installing breakpad exception handler for appid(steam)/version(1603487799)
[1102/145523.884348:INFO:crash_reporting.cc(270)] Crash reporting enabled for process: renderer
Installing breakpad exception handler for appid(steam)/version(1603487799)
Failed to init SteamVR because it isn't installed
ExecCommandLine: "'/home/tyros/.local/share/Steam/ubuntu12_32/steam'"
System startup time: 14.65 seconds
Warning: failed to set thread priority: set failed for 4: -1: setpriority() failed
Warning: failed to set thread priority: set failed for priority 4
Warning: support for elevated priorities is most likely unavailable, suppressing future warnings
[1102/145525.936417:INFO:crash_reporting.cc(270)] Crash reporting enabled for process: renderer
[1102/145526.011350:INFO:crash_reporting.cc(270)] Crash reporting enabled for process: renderer
Installing breakpad exception handler for appid(steam)/version(1603487799)
Warning: failed to set thread priority: set failed for 4: -1: setpriority() failed
Warning: failed to set thread priority: set failed for priority 4
Warning: support for elevated priorities is most likely unavailable, suppressing future warnings
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
BuildCompleteAppOverviewChange: 578
RegisterForAppOverview 1: 158ms
RegisterForAppOverview 2: 161ms
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
ExecuteSteamURL: "steam://open/downloads"
ExecuteSteamURL: "steam://open/downloads"
Installing breakpad exception handler for appid(steam)/version(1603487799)
Installing breakpad exception handler for appid(steam)/version(1603487799)
`
Still I do not know why it refused to start at first, except some uninstalled manifiest warnings.
Anyhow Steam is now running, I'd like to get some intel on what has gone wrong, should anybody be able to.
Thx!