What issues did you have with it?

I use an FP3 personally, on Android 10 at the mo (13 is available, but i'm planning to move to Lineage instead), haven't experienced anything I would describe as a dealbreaker - especially compared to my previous device which was an S5.

On paper it looks rubbish, but compared to my S5 it's night and day. That said, I wouldn't suggest any 'sustainable' device to someone using a mainstream flagship like an S23 etc, as 'sustainable' devices typically always pick older components with the longest service/support life, not the latest and greatest. It's a compromise I am fine with, but people who are very heavy/demanding power users should 100% look somewhere else or just keep using their current device IMO...

Actually, on the topic of FP issues, particularly for the target audience that i is maybe likely to use more FOSS apps on their device, is a bug that mis-clicks after a lengthy amount of time spent in apps that use Jetpack Compose for the UI (like Jerboa and Kvaesitso). I'm not familiar with that tech at all though so this is completely out of my depth. I've only ever noticed fellow FP users complaining about it. The fix is to force kill the app, which can get a little bothersome