Total posts : 45366
Any installation connected to the AC ground system for use as an RF ground would exceed the limit permitted by FCC ¶15.219(b). Unless of course you isolate the AC ground at the receptacle and connect it to a non-radiating ground.
So, your choices are – earth. That rules out most any place besides outside or a house on a slab.
You can’t back-pedal this. I agree with you. Plugging into the typical AC ground would create “installations exceeding the limit permitted by FCC ¶15.219(b).”