The desired alternative is not Matrix simply because privacy-conscious, open-source ecosystem vs. proprietary solution is not the goal. Matrix would still generally be terrible for support. What people want is publicly searchable content that is ideally indexed like a wiki. Many will happily settle for issue boards or even forums though. Discord has pathetic search capabilities in comparison to any search engine and has no way to properly and publicly backup information that is posted to the platform. With a website of any kind, one could clone the site for mirroring or simply get a web archive service to crawl relevant sections.