I agree that 1) and 3) are hard, but you don't have to do 2) like you said. Asking strangers is not that hard, and most people I know don't find it annoying to be asked. Just do not ask for an unbounded amount of time.

Ask specific questions. Even to strangers. Many will be flattered you asked and will answer. Some will tell you that they do not have time or energy right now. Many will not answer at all (1).

How do I know? I do ask strangers for advice. And I am open to questions: From time to time, I publicly say that on Twitter (like "Reminder: Ask me anything about code quality, technical excellence, TDD or freelancing. DMs open"). I get interesting questions from total strangers, and I answer them as best as I can.

So, maybe also do search for people who offered their help to strangers in the past.

Maybe you will not find a mentor right away by asking strangers for advice, but maybe you can be able to evolve a conversation into a form of mentorship.

(1) If someone answers in a rude or condescending way, block them.