How to handle swear words in quote / transcription?
If you're quoting someone, quote them as they said it. We're all adults. In the literature world, we quote swear words and other potentially offensive things all the time and no one bats an eye. I've no doubt other fields are the same.

Personally, if I saw an asterisk or similar, I would presume you interviewed them via chat or email, and they actually self-censored. If it were a printed text, I'd think it a part of the edition you used.