I went looking and seaching, and didn't find a Free Discourse Forums host so far.
Best I found was a professional install and config, done for you, costing $150 USD one time fee. This is installed into a Digital Ocean droplet small server, which is a $5 a month service fee.
Screenshot from : https://www.literatecomputing.com/discourse-installation-packages/
Discourse.org also says you can do it yourself -- and provides this page to guide :
https://blog.discourse.org/2014/04/install-discourse-in-under-30-minutes/
A Digital Ocean signup with a FREE one month of service deal -- https://m.do.co/c/a5bf212d9a92
Although staying here and using the already running service is the simplest option of all.
The official discourse support channels are a joke. I highly recommend you stay away from it. Its open source software so I cant really be too mean on them, but they are some oily business people on that forum in my expiernce.
They intentionally design the installation docs to be very narrow and rigid so if anyone wants to install discourse in a cheaper or more professional setup they have to pay one of them a fortune to do it.
I was stuck redoing a lot of discourse to get it work in docker and with no help from them. To even ask for help would have gotten me banned (I was warned when I tried).
Its worse, the install is non standard docker. It is done in such a way it cant exist with other docker installs on the same box so it absolutely must be run as the only service on its own box...
It really is horrible.
Funny thing is they insist they dont force people to install it that way (and banish them if they try to help people with alternative installs) because "we want you to be happy with your instance and we want it to just work"... well guess what, I'm not happy!