I subscribe to a bunch of Yahoo discussion groups, all technical in nature. However they really messed up the format a while back if you try to use the web site instead of the emails. Searching is almost impossible.
I’ve used Yahoo mail since about 1998, but I slowly transitioning to Gmail. Who knows what plans the new owners have. Also, I hate the auto start videos that are now displayed on Yahoo mail. That’s one of the main reasons I’m leaving.