After 2 days of banging my head against the wall and realising Discourse doesn’t like apex domains (and yes, i’ve read the article on the forums explaying that) i was able to install on a subdomain.
You could achieve that in one of two ways (both consist of a redirect)
You could use cloudflare page rules to redirect example.com to forum.example.com or
You could set up nginx to perform this redirect for you. I believe discourse’ internal nginx is configured so that all requests coming in are redirected to discourse hostname. See: Redirect additional domain(s) to your Discourse instance
and Congratulations on getting your new discourse up & running.