I recently built the Ubiquiti Unifi Controller on my Raspberry Pi2B this week.
I had been using an HP SFF with Win 10 ENT, and huge resource waste and interruptions on my guest network due to Windows updates. I have a single long range AP but it serves 15 users over 3 SSID's of which one is a visitor voucher hotspot.
I used an 8Gig Micro SD, Raspbian 'Buster' with the latest version of Unifi for Pi 5.11 from September 2019. The result is excellent, the community is a huge resource for configuration!