Rather delayed but I came across this while searching for the same question. Figured I would post an answer.
I installed the Unifi controller along side my Hassbian install last night. v.1.3.2 of Hassbian and v. 5.7.23. of the controller and a Pi3B.
Installed and running without issue. CPU usage is up a percent or two (3-4% total now). RAM was ~20% before the controller install, currently sitting at 56%. Still seems to be a bit of headroom.