Haven't booted my pc for a while, suddenly this showed up today?

That's not an error. That's the boot menu. You probably hit a button while it was starting. It allows you to enter different boot options or when you have multiple operating systems installed you can choose which one to start.

Just select the first entry and hit enter.

This isn’t an error, it’s the GRUB boot menu

tl;dr is just use your arrow keys to select the top option and hit enter, and you’ll be fine

😹😹

What's the difference between the first two? Ostree:0 and Ostree:1

Ah, didn't notice that. I'm not super familiar with Bazzite but it essentially has two versions of the operating system. Updates are written to wherever you currently are not. That way if something broke with the system you could go back to the working version.

No idea how you can find out which the "current" version is supposed to be. Probably still the first one in the list. Either way it shouldn't matter so much because an update and a reboot should put you into the right one.

TIL! Thanks. I find whole concept of an immutable setup so fascinating.

Ye, it's weird. Apparently my Asus bios changes my secure boot mode back to default (windows uefi) whenever it updates the bios...

No, it just gave the error nomatter what I picked
Edit: did not see the error message dissapeared from the screen when I took the image xD

For some reason, it updated when I took the photo. Everytime I selected one of the options on the image, it just gave me a "boot error"

check your laptop battery health. Asus laptops will randomly set the bios options back to default settings if the battery is causing issues or dying.

Its a desktop 😬

well in that case, check your cmos battery.

Bazzite installs updates by making a snapshot of the entire system and then installing a new system image beside it.
That way if there's an issue with the updated system, or you broke it, you can just boot into the last known good one.
Ostree:0 is the current system and Ostree:1 is the previous version.