Comment 9 for bug 1901272

I also just installed on a pi 4 and had the same issue -- devices worked but would not persist across reboots, and then successive re-adds were... strange, unreliable, etc. Lots of "it appears to work but doesn't." Tried the PPA packages and it worked at first, but was seriously inconsistent at adding and removing devices. I downgraded the PPA packages back to originals and still couldn't reliably add devices. I re-upgraded to PPA packages and the bluetooth was essentially working less than ever. Since it felt like a software issue, like configurations and "sessions" were being munged, I killed BT, searched around and wiped out /var/lib/bluetooth/* (which appeared to have multiple base addresses???) and then I was able to clean out gnome's ui and re-add and things now persist across reboots.

To me, this seems like the PPA fixes the issue, but the original packages created a state where there were multiple stale / conflicting states in /var/lib/bluetooth that you must disabled bt, clean, then re-enable / reboot and things work. It almost feels like the original packages had the BT adapter changing addresses each boot or similar.