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This is for research/curiosity purposes only but yeah some of those sites are operational albeit crawling with cops. If you don't know how to use PGP then learn. Verify your links and crypto addresses every step of the way and don't get lazy, get links from a legit source, encrypt all your messages with PGP and perhaps use privnote too. Basically read some guides and don't be a retard, and VERIFY, I can't stress that enough. On a totally unrelated note Monero is more secure than bitcoin just fyi but you still shouldn't make any purchases by sending your crypto directly from an online wallet on the site you bought it to the merchant as it's probably connected to your bank card and ID, as a general rule it's more secure to put it in an offline wallet first.
Another unrelated note, customs/border officers are far more thorough and do not hesitate to rip shit apart and confiscate anything that seems weird, whereas regular post that stays within the country isn't scrutinized very much. Theoretically those are a few ways a person could poke around on onion sites while minimizing the chance of getting scammed or arrested.