As a maintainer of a small open source project I have to disagree. The hurdle for someone to join Discord and ask a question is much lower than signing up to a custom forum and posting there. I also love interacting with people that use my stuff. Makes me feel warm and fuzzy to see that people are actually using it. I can see the other side of course. There are a few things that are repeated questions or useful conte…
Perhaps Matrix is an option as well. It's open source and open (decentralized) - and can be indexed by search engines if you set the discussions to public Matrix can also be bridged to Discord, so you wouldn't split the community.
There's been quite a few cases where the only hit for an obscure error message I could find was some kind of Gitter chat, but I've learned to not even bother with those results.
Search engines also have trouble working with chat messages and even modern forums like Discourse. When you click a link you will have to spend significant effort trying to find the highlighted text, something that was a lot easier back in the static HTML days. You have to let Javascript do its fetches and queries to get the information supposedly found somewhere in the page, and it doesn't always load so you may need to scroll to the end to get the rest of the discussion, making "find in page" useless. Discourse tries to solve this by providing heir own control+f handler which is somehow even worse.
I understand the want for more and quicker interactivity. It's a better experience for the person writing the question or the response. This comes at a massive cost in readability and knowledge transfer, though.