Welp, that took nearly 13 hours to fix. I was able to recover everything, as I am luckily stupidly paranoid, and always make a Timeshift snapshot prior to updates, or any real, non-standard-pc-use stuff, like installing random dependencies for niche programs, etc. (Bless you, BTRFS!)
Literally no idea if my situation is likely to ever be shared by someone else, but I might as well explain what happened.
During a full system update, the OS froze, and hard crashed. When boot, I just got a blank screen.
Things I did to fix it:
Get a USB drive with EndeavourOS on it, then boot into that.
Do the recovery steps listed in the link, but get absolutely confused since my install is using BTRFS, and had CSM enabled in the bios.
Even more confusing, was that my bootloader (grub) was just… completely gone, without a trace. From what I read, I figured that I probably needed to (after repairing and finishing the interrupted system upgrade) install another bootloader, since repairing the OS update didn’t add it back. (Made a new partition just for it, etc.)
I then made a mistake, which cost me quite a few hours. To get an output from my GPU while in Linux (apparently pairing an ancient 1060 with brand new components, X870 MB, and a 9950x CPU, causes some incompatibilities…,) I needed CSM in the bios enabled.
Thus, I specifically install a bootloader that was compatible with CSM enabled machines. What I forgot… was that I made this install on an older desktop, which didn’t need CSM enabled to get an output. Oddly, back when I installed the NVME drive into the new comp with CSM enabled, my install booted fine without me having to do anything. So, after all of that, I still didn’t get grub to boot.
Recalling this fact, I installed the correct bootloader (including doing the proper mounting steps for actually having a efi/UEFI bootloader/install,) but still no boot. Though it did show an underscore, instead of just a blank screen at that time.
Since my CPU has its own IGPU, which I could get output from via plugging into the MB, I decided to randomly disable CSM. Despite it booting just fine with CSM enabled before, the grub finally booted once it was disabled.
However, it wouldn’t let me boot into my install of Endeavour OS, since it was likely still broken in some way. But my snapshots worked just fine. With the one that I made prior to the update used as the restore snapshot, I did so. (Via Timeshift BTRFS snapshot. Yes, I did forget about snapshots right up until this point…)
Booting into the snapshot was perfect, with all my files intact, etc. But, when I rebooted, it would just go to grub rescue. Nothing I did inside it ever fixed the bootloader.
So, back to the live usb I went. The bootloader partition was actually there this time, but must have been broken in an odd way, which only manifested after the restore and bootloader was misplaced, or something. Once I got through the confusion of installing Timeshift on a live usb environment, then doing the restore, I’d still get booted back to grub rescue. Though I did backup prior to even starting the update, the bootloader was apparently still borked. I just installed a new one, again…
After installing the grub once more, I was then able to boot into a properly working Endeavour install, with no data loss at all. The weirdest thing… is that I no longer needed CSM enabled to get an output from my GPU when using Linux. Maybe installing Nvidia drivers fixed it, or a Linux update did that, and I just didn’t notice until now. (No output from GPU prior to grub, but that is likely due to it being too old when compared to the other components of my build. Either way, I’ll be switching to an AMD GPU when I get the money to do so, haha.)
Long essay aside, a large portion of this little adventure could have been avoided with better knowledge of Linux. Especially since I wasn’t aware that you could restore a snapshot from a live USB environment until over six hours in… But I have only been using Linux for 4 months now, and I am not that technical. Thanks for the help, as that article did get me started on the right path!
(Sorry if any of this is pointless/rambling. I’ve been up for over 20 hours now, and just wanted to explain how I solved this issue, regardless of how not awake I am atm, oof.)
