There's this ongoing effort by HN user sirobg:
Ask HN: What should I do with meet.hn? - https://news.ycombinator.com/item?id=42410582 - Dec 2024 (168 comments)
Show HN: Meet.hn – Meet the Hacker News community in your city - https://news.ycombinator.com/item?id=41539125 - Sept 2024 (372 comments)
I've been thinking for years about building support for offline meetups into HN itself somehow.