I can't say I've given Jellyfin a proper try (as in using it and the clients exclusively for a long period) but we have been using Emby for quite a while before I knew it existed.
If I'm not mistaken Jellyfin is actually a fork of Emby so they're pretty similar, but one is a bit older.
Is there a handy list somewhere to defed from? I don't expect them to gain any traction unless they had an existing user base before, but would be nice to keep communal running tab.
Many places refer to secure email when they mean a portal that function is more like a private chat app. A lot of them are even sold as 'secure mail' but don't use anything resembling SMTP.
Instead you log into a page, and send a message to the specified recipient who might have an email style address on it, or maybe on the backend it uses their email system for authentication even.
I was probably using Emby already by then, had bought a lifetime license since it didn't require bouncing things off and outside server like Plex did (or was it that Plex was a renewing subscription, I forget) , so it just stayed out of inertia.