Honestly I kind of hate how M3F went down and then seems to be fragmenting across many communities. So many resources and knowledge lost... Maybe at some point we'll all pick a platform but at this point there are a couple that I've found..
I think Ian 'Obioban' had something to do with the creation of this one. More E46 focus but I've seen posts from all different gens there..
https://nam3forum.com/forums/
And I think Brett 'Braymond141' created this one - seems to be a pretty heavy emphasis on the e36 platform:
https://www.mforum.net/
hope that helps