I doubt anyone else is coming back to read this other than you if you have notifications on, but Snopes, based on photographic evidence of intact teleprompters and other evidence, is willing to rule the teleprompter glass shard theory as "False".

They do note the recent statement from FBI director who said: "There's some question about whether or not it's a bullet or shrapnel that hit his ear", so I guess it's still not clear it was definitely a bullet but yeah, teleprompter glass seems to be out.