[2021] where can one go to post a group link?

You can search for groups, players or promote your own server in the LFG subforum.
Read the subforum rules before posting!

Posting group links in general is not allowed and counts as advertising.

You can promote your server without giving a link. Links are not permitted per the rules in LFG.

Yes, view the Looking For Group subforum to see examples.

Follow the rules listed here: https://steamcommunity.com/app/892970/discussions/3/5879990700813169065/

If you still have questions feel free to ask, otherwise I'll close this thread later.