https://github.com/Jarred-Sumner/bun is an example of a project that embraces Discord as a forum. To get any reasonable community knowledge, you must join the server. And the server isn't indexable by search engines, of course.
It even recommends getting help in Discord when an error happens
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.