I also had a slightly rough experience. I started my upgrade from 22.04 -> 24.04 and walked away. I came back to my system frozen on the Plymouth screen. After

I also had a slightly rough experience. I started my upgrade from 22.04 -> 24.04 and walked away. I came back to my system frozen on the Plymouth screen. After trying and failing to get into a TTY a few times, I booted into recovery mode, re-ran the upgrade, and it actually worked. That was a lot rougher than my experience upgrading from 20.04 -> 22.04, which went off without a hitch.