It's on a lot of european 79 shows where he did it. I don't think you can count it as a live performance of Fun It.
Or else they also played Dead on Time, Chinese Torture and Let me Out live
I have a post on my channel link of Freddie singing a few lines of Fun It before KYA in Montreal 1978.
I have a post on my channel link of Brian doing Chinese Torture during his solo I believe in 2005.