Welcome @jokibitzer. You can find out about purpose of this community, and the forum categories in Welcome to SocialHub introduction topic. Fediversity may be a good category.
“How do we bring federated forums into the Fediverse as open alternative to Discord & Slack?” might be a good topic for discussion. There are 3 forum softwares discussing an integrtion to the Fediverse already. They are Discourse, Flarum and NodeBB. (Note: Some people call forum-enabled Fediverse the Threadiverse.)
This community is not so generic that a “FOSS projects shouldn’t use Discord” is on-topic here.