Google's John Mueller again said that dropping links in forums for SEO purposes won't help you rank better in Google. In response the Reddit thread question "Is Forum Posting Still Work As Link Building Method in SEO?" John Mueller said "No."
The person who wrote the question added "I want to create good backlinks for my website is forum posting plays a vital role in the off-page submission of SEO." In which John posted his two character response, "no." Well, three characters if you include the period.
Of course, there are several folks in the Reddit thread that claim these links do work. So you can try it if you like, but I suspect there are better places to try to get "natural" links than forum threads that are likely nofollowed by default anyway.
Just for some history, John said this also in 2014 and 2018. So it was time for me to cover him saying it again in 2021.
Forum discussion at Reddit.