Hi

Has anybody been able to perform a Facade scan with either DJI Pilot, GO 4 or with a custom SDK App? I've tried UgCS and it appears to be ok but is a little pricey.

Drone Harmony can do facade scan.
Check their pricing - UgCS is cheap ...

The typical way to do it is with Orbit or POI flight paths at multiple altitudes as needed to fully cover the facade. If its more than just a facade then an orthagonal line or grid survey is good to do as well.
Unfortunately DJI does not inlcude POI as an option for the new flight controller software on the P4P RTK...