How are you configuring this? I checked for Jellyfin and their are third-party plugins which don't look too mature, but none of them seem to work with apps. qBittorrent doesn't support much (actually I may be able to put reverse-proxy auth in front... I'll look into that) and Metabase locks SSO behind a premium subscription.
IDK why but it does seem that LDAP is much more widely supported. Or am I missing some method to make it work
I do use a reverse proxy but for various reasons you can't just block off some apps. For example if you want to play Jellyfin on a Chromecast or similar, or PhotoPrism if you want to use sharing links. Unfortunately these systems are designed around the built-in auth and you can't just slap a proxy in front.
I do use nginx with basic with in front of services where I can. I trust nginx much more than 10 different services with varying quality levels. But unfortunately not all services play well.