“Tangible” is one form of evidence.
In a courtroom witness testimony is allowed as one form of “evidence”.
There have also been alien implants as well as ground traces of craft if that is your thing.
Radar tracking is another form of “evidence”—lots of that.
Then there are UFOs that have turned missile silo systems on and off in front of human witnesses—that is another form of “evidence”.
If you don’t like those there are cattle mutilations, crop circles etc etc etc.
There is some fakery in all of that—but again it all depends on what you count as “physical evidence”.
“There have also been alien implants as well as ground traces of craft if that is your thing.”
that’s the best you can do? After more than 75 years? Pathetic.