Hosting for the public, it’s honestly going to depend on how many users you are going to have. Pretty much anything that is light on bandwidth should be doable. Websites, blogs, wikis. XMPP chat servers might work. Matrix might work as well. Adding to your seeding idea, you might seed torrents for any Linux distros you happen to like or build torrent seeds for projects with larger download sizes. I seem to recall a project that would enable you to seed peertube channels as well, though I can’t find the project right now.

If it’s just you and maybe a few family and friends,say over a mesh VPN, what ever you want, though video streaming may be a bit much for that bandwidth. Any other type of personal media should be very doable. Books, music, that sort of thing.

Lack of trust, for the most part. I’ve been screwed over a few too many times for me to rely entirely on someone else. Whether it’s Audible claiming I never bought an audiobook I knew damned good and well I did buy or seeing someone else getting their life made difficult by Google, Apple or Microsoft, or “friends” and family making life difficult, I’ve learned the hard way over the years I can’t rely fully on anything not under my control.

I would take a look at TeamSpeak or Matrix.

Of the two Matrix is probably the closest to Discord.