I dont know How to make a forum like TMT forum, and i wanna know so bad!!
I use a popular open source forum software called Discourse. You’d require a server to run it on (and since it’s public facing, you shouldn’t just host it on your home IP address). I use Hetzner which is exceptionally affordable. You’d also need a domain name - I currently use Porkbun but namecheap or any of the others should all work just fine.
All told, expect to be paying up to $10/month (but potentially less) to host everything.
What are you interested in hosting a forums about?