I’m doing some detective work trying to scrounge up and old friend from back in TBC. It was a human priest named Chandra, we played on the Nagrand-EU server together before I switched to Horde. I looked up their character on the Armoury and they’re level 48, which is above what used to be 110 before the squish, so they’ve definitely played sometime in BFA or prepatch. I’ve also managed to peep their Achievements, but that sends a bad omen - they recently got achievements for reaching max level on alternate characters. I don’t know their full BattleTag number and everything and I don’t immediately see any way to look up alternate characters of an account anywhere.
The best I can think to is to try and check regularly if they’re on the Priest character with a /who Chandra-Nagrand and hope to get lucky, but if anyone has a better idea or completely coincidentally happen to know the person please let me know.