Gosh. I wish I knew. This thread is rife with alternatives, so other's guess is as good as mine. The unifi wifis I have running are still good and work extremely well. So my suggestion is to keep using them, but only if you host the controller software on your own hardware (I'm using RPi 4 as stated) and only if you avoid their cloud solution(s). (This IMO).
I am still looking for alternatives when the time comes to replace mine. Which I'll be forced to replace once/if they completely nerf the self hosted on self hardware options.