It was always throve when I was growing up.
Thriven is the past participle.
The forms “throve” and “thriven” imply a “strong” (irregular) verb. “Thrived”, “thrived” would be a weak (or regular verb.) “Strong” verbs are relics of of older Germanic verb forms. Swim, sing, hang, ...
I’ve thriven plenty of times.
Right now I use a Challenger to Thriv :)