Ubuntu Studio 20.04 LTS crashed and won’t boot, boot-repair didn’t fix it

good people, I’m having a little trouble.
I’m not a complete tool, but I’m definitely on the beginner side of computing.
Built my desktop in May (AMD Ryzen 3 3200G, Gigabyte B450M DS3) and been running Ubuntu Studio as the only OS without much trouble at all.

Today I was plugging a usb lamp in the back of my machine and when I got back up to the desk, my screen was blank and all was dead.
Since then, I can’t boot the OS and even when I press escape to get to Grub, I can’t edit it and only see lines with “grub>” or something similar.
I booted the system from my bootable usb stick (“try without installation”) – I can only do it in safe graphics mode.
There are few errors appearing:

  • Initramfs unpacking failed: Decoding failed
  • pci: 0000:00:00.2: AMD-Vi: Unable to read/write to IOMMU perf counter.
  • (drm:amdgpu_init (amdgpu)) ERROR VGACON disables amdgpu kernel modeset
  • sd 9:0:0:0: (sdb) No Caching mode page found
  • sd 9:0:0:0: (sdb) Assuming drive cache: write through

In the safe mode (running from the usb stick), I tried boot-repair, which didn’t work.
This is the generated pastebin: https://paste.ubuntu.com/p/4vQttQtWc2/

I managed to save some important data on the harddrive on the cloud, so I’m ready to reinstall the OS and start from scratch, but is there anything else I could do before being this radical?

Thanks a lot.