Tesla did try to prove you could use electricity through the air remotely but wasn't successful he lost all his money trying to prove it and died poor.
It has nothing to do with flat earth theory though and i doubt he believed the earth was flat he was way too smart for that.
Tesla is very often misquoted by flat earthers. It is very, very apparent and clear that Tesla did not believe in a flat earth at all. The "firmament" quote that is most often misquoted was a metaphor. It's typically taken way out of context, and even more often, it's edited and modified from its original text.
Tesla, who used the word "globe" to describe the earth repeatedly, consistently and reliably says everything.
"Globe" is very clear. It isn't "disk with a dome on top".
Just another deflection, using false information.
And what about this ice wall around the planet that can't be gotten over. 35,000'? 40,000'? No aircraft can get over it? Why don't we hear about planes crashing into this "firmament", or ice wall, ever?