Standards like fast roaming are fraught with issues.
And at one point they added call homes/telemetry. I think the 5.x code.
That is to say they have always been buggy in one form or another. More so than other vendors like Aruba or Cisco, I’ve managed both at campus scale in a previous life. I wouldn’t put them in an enterprise but a smb or soho deployment sure.
When they did the call homes/telemetry I created some firewall rules for the controller. The controller can only talk to the Ubuntu repos. Aps are on a private vlan with no internet. I only open the controller up for Ubnt upgrades and then shut down the rules and disable the ubnt repos in sources.list.
If I were someone new in the market I would look at the ruckus unleashed platform for wifi. You can get aps with extensive features cheaper, especially grey market.
I would and have avoided UBNT for all routing and switching.