>>247555-youtube "about me"s for channels often have their real email. Also check archived versions of the youtube channel page.
-generally with oxing and specific with emails, weirdos are less vigilant about PII the further you go back. So look for early accounts/names, I've found emails in chives for nuked twitter accounts, personal websites, reddit comments.
-info in the description for yt videos, artwork, comments on instagram, etc. Maybe they re tight lipped about the email these days, but that 4th DeviantArt drawing xhe did was captioned "open for trades- email me at turd@gmail.com!"
-low odds of success, but trying variations of name or username. Bob michaels aka SonicFan541 could be Bmich541@gmail.com, that kind of thing.
-also with breach.vip, if you know and confirm an account was in a breach, you can find the email through that path. ex: you found their old wattpad name, now search that username they only used once and you didn't think to check before, and bam there's the email.
good luck!