Discord isn't a forum.
GitHub even has a Discussions feature in case you don't want to set up a forum.
It's just awful that the project has almost three times fewer stars and issues on GitHub combined than they have members on their closed Discord server.
Discord server:
- Isn't indexable by search engines
- Makes you go through some antispam bots
- Makes you join yet another server (number of which is limited)
- Creates unnecessary interactions, for example server admins that love doing @\everyone for no good reason
- ...