Dear forum/site admin,
1) you seem to have changed the URL scheme sometime from:
2) and not have any specific redirection from OLD to NEW but instead simply redirect to https://forum.openmediavault.org
3) and seem to be still present with the OLD scheme in some search engines (i.e. I came via DuckDuckGo.com)
This certainly looses you as the site operator a lot of good traffic or from the perspective of an interested audience "hinders many people from getting relevant help/content".
Concrete example I encountered:
just redirected to the home page https://forum.openmediavault.org
So as a tech-savvy user I went back to DuckDuckGo, copied the link manually.
Then opened an arbitrary thread. And simple replaced "NNNNN-the-title" with just "NNNNNN" which as a short-URL then gets expanded to the SEO optimized full URL:
But only a minority of users will do that.
So it may be worth to write a URL-rewrite-rule from OLD to NEW scheme to get that full visitor potential.