Huge thanks to the Linuxserver.io team for this Docker container. I just set it up on my existing Unifi network and migrated from my old controller (running on a DigitalOcean cloud instance) using the Unfi controller's Site Export Wizard. The process was flawless, and I had all of my devices up on the new controller in about 5 minutes. Both controllers were on 5.12.35, and all devices were up-to-date, so that probably helped a lot.