I barely say "got" or "gotten" and thus I'm trying to add it to my vocabulary. I live in the United States and fully understand they are best used in informal context.
I see a load of resources but some seem to contradict each other.
https://www.grammarly.com/blog/got-gotten/ : If you live in the United States or Canada, you will probably choose gotten as the past participle of get.
https://www.oxfordlearnersdictionaries.com/definition/english/get : North American English the past participle gotten
https://oneminuteenglish.org/en/have-got-vs-have-gotten/ : Have got and have gotten are different
https://english.stackexchange.com/questions/120721/have-vs-have-got-in-american-and-british-english : too academic and beyond my comprehension
"Gotten" versus "got" : didn't mention "must"
At any rate, in American English in informal speech,
when I need to say "I must leave now", can I say "I have got to leave now" or "I have gotten to leave now"?
when I need to say "I have bought an avacado", can I say "I have got an avacado" or "I have gotten an avacado"?