GrapheneOS is an option. The Pixel 4a is not really supported any longer with the current branch but…it’s GrapheneOS so it’ll be secure(ish). https://grapheneos.org/faq#supported-devices.
Do keep in mind GrapheneOS has some weird, deal-breaking issues, like RCS not working and other weird, random shit like that.
Did your computer lose its bios settings lately? Check to see if it’s set to ahci and not raid if using a single, non-raid disk.
You can try some of the suggestions at https://www.linuxquestions.org/questions/linux-newbie-8/how-can-we-fix-this-no-irq-handler-for-vector-4175692269/, too.
Good luck