In 2020 when I was upgrading to Ubuntu 20.04 LTS, a similar thing happened to me where the upgrade simply froze for 1 hour and upon rebooting the whole installation was fucked. This was the 3rd time when this happened over the years (I've been using Ubuntu on and off since 2008). I'd finally had it with Ubuntu and I quickly flashed a USB drive with ArchLinux, used it to salvage the data from my broken installation ,since my /home partition was still intact and then switched to Arch as a daily driver. Have had very little problems since