Absolutely agree that hiding knowledge behind a paywall is crappy. I hit that issue so many times with Red Hat that I standardized on debian variants.
Searching, while a function of any modern forum, is easily bypassed with a modern search engine / crawler. Unless the forum admin takes the unlikely step of disabling web crawlers on their site, you can pass the site:<website> filter into your search. For example: https://duckduckgo.com/?q=subtitles+site%3Aforum.jellyfin.org&ia=web shows forum posts regarding subtitles.
+1 for Joplin with Nextcloud / WebDAV sync.