Little backround info from thread
https://discuss.getsol.us/d/12124-unable-to-add-load-options
But, let me try again, since there are some things that I've figured out, and situation is a bit different.
Before I enabled secure boot, boot failed, using "Solus Linux Bootloader" at EFI. I got these messages:
Could not create MokListRT: Volume Full
Could not create MokListXRT: Volume Full
Could not create SbatLevelRT: Volume Full
Could not create MokListTrustedRT: Volume Full
Something has gone seriously wrong: import_mok_state() failed: Volume Full
I applied these guidelines:
https://unix.stackexchange.com/questions/774195/could-not-create-moklistrt-volume-full-etc-when-trying-to-boot-almost-any-distr
...and managed to clear these "EFI variables", so the Volume wasn't Full anymore. After that, Enrolling the Solus certificate was successful, and boot also did not fail.
But, this lasted only to the point when I updated the machine (first with discover and when that failed, pkgkit-something failed, then got it done with Solseek!). I noticed there were microsoft/certificate stuff or whatnot in update-packages. After this update, boot failed, with same error list as above (MokList etc).
So, I had to clear those "efi-variables" again, which isn't convenient at all, since I have to create admin and user passwords again at efi, then clear them afterwards.
I figured out I have these options too:
Boot is successful, using boot entry at EFI called "Linux Boot Manager", but with these messages:
Without secure boot;
"Unable to add load options (i.e. kernel command) line measurement to PCR 12: Volume Full
EFI stub: WARNING: Failed to measure data for event 1: 0x800000000000000b"
With secure boot;
"Secure Boot Violation
Invalid signature detected. Check Secure Boot Policy In Setup.OK."
(OK -> ENTER, machine still boots up! ...WHAT, WHY?)
Question 1: Do I have to clear efi variables, manually, every time there's an update containing certificate stuff, if I want to use secure boot?
Question 2: What is this Linux Boot Manager (compared to Solus Linux Bootloader), and why these two options?
Answers, comments, educated guesses are welcome. My brain hurts.