Reddit is the most popular online discussion forum in the US. Searching brings up hits in "subreddits" where members can post and comment.

Medium is an online platform created by a co-founder of Twitter (X).

The link provides a search of the 4chan discussion board site. 4chan.com provides topical discussions but does not have a search feature. Use the linked search feature to search the discussions with your topic. DISCLAMIER: 4chan includes a sizable amount of adult and offensive content.

Ars Technica largely focuses on technology although it also branches into news and some popular culture.

SaidIT describes itself as a slightly modified and improved version of Reddit, and functions very much the same way.