I only used solus' help section.
Download ISO (did that 5 different times in 12 installs).
-burn to disk using rufus. make sure GPT, FAT 32, DD, UEFI. restart, make sure usb key is first boot. load solus, (can't load kernel) but still loads. I'm actually typing this on the booted USB stick.
created 512 mb efi partitioned hard drived. Also have used Windows and Manjaro's EFI partioned for the boot loader. Tried installing along side windows, tried installing along side manjaro, tried installing on 3 different completely formated hard drives/SSDs. many different errors but the most consistent is, everything loads, and when it comes time to unmount, I get the error that I listed about. rinse repeat. a few times it was couldn't find EFI, or EFI was too small, but like I said, I've installed it on completely empty hard drives and allowed solus to create the EFI, and I also created it myself to no avail.
I have Core I9 7900x, 2 NVME, 2 SSD, 2 Hard disk including one WD raptor, 64 gb Ram, Geforce 1080TI. I've last bought a computer in 2000, always have been building and rebuilding computers since, but only windows. Recently, I've dabbled into linux. As I mentioned, I currently am using Manjaro, which other than an issue with getting my wireless card to play nice, it worked just fine. I really wanted to give Solus a try, but can't get pass the install. Only once did it install, but it then locked up when I tried updating my nvidia drivers.
At this point, I might just decide to go the route of Manaro Budgie, or Ubuntu Budgie to experience the Budgie desktop.