IIRC, a normal prune doesn’t get rid of those, only the --all prune does that. The normal one only erases images that aren’t associated with any container.
The Android app works well. I rarely have issues with it, except when switching back and forth between the web player and and the app, when it sometimes doesn’t properly sync progress fast enough.
On one hand, it’s a good thing. On the other hand, it’s not that surprising that the group specifically dedicated to biodiversity is slowing biodiversity loss.
That’s what I use, but I don’t think anybody would say that next cloud is a simple app.