Thank you for pointing me in the right direction, I would have been searching for the wrong things for a long time. That sent me to this forum post which seems to be exactly what I’m looking for: How to chroot Garuda Linux
But now I’m a bit worse off than I started. Entering the chroot environment was easy enough. I was able to mount my boot partition with mount /dev/sdb1 /boot, and update-grub worked fine. There was a “Kernels not found” message which I wasn’t sure was an error, but googling turned up no results so I figured it’s normal. I rebooted and behold, I had a grub entry for Garuda Linux again! But it didn’t boot.
Booting `Garuda Linux (on /dev/nvme0n1p1)`
error: no such device: ca2fa708-e61a-4167-9312-ffbc040fa3bd.
error: filename expected.
Press any key to continue...
Failed to boot both default and fallback entries.
Press any key to continue...
So I entered chroot again, and this time installed grub with grub-install /dev/sdb. I ran update-grub and got the same results as last time, seemed fine. I rebooted, and this time there was no fancy grub splash screen waiting for me. It went straight into grub rescue mode.
GRUB loading...
Welcome to GRUB!
error: no such device: ca2fa708-e61a-4167-9312-ffbc040fa3bd.
error: unknown filesystem.
Entering rescue mode...
grub rescue>
I found this forum post about reinstalling grub: Cannot Reinstall Grub Bootloader - #4 by FGD and it mentioned that the user had a GPT partition table, so they should be installing the UEFI version of grub instead of the legacy BIOS version. My boot drive is also partitioned with GPT, but I was using the legacy BIOS version before so I don’t know if I should be using the UEFI version. My motherboard might not even support UEFI.
I also saw in an askubuntu question that when installing grub, you have to point it to a location to read data from the hard disk at the beginning. I am not sure how this works in a chroot environment, or when the root partition is on a separate drive. I’m not sure where to go from here.