The general principle is called single sign on (sso).

The idea is that instead of each all keeping track of users itself, there is another app (sometimes called an identity provider) that does this. Then when you try to log into an app, it takes to the to login of your identity provider instead. When the IP says you are the correct user, it sends a token to the app saying to let you access your account.

The huge benefits are if you are already logged into the IP on a browser for example, the other apps will login automatically without having to put in your password again.

Also for me the biggest benefit is not having to manage passwords for a large number of apps so family that uses my server have 1 account which gives them access to jellyfin, seafile, immich, freshrss etc. If they change that password it changes it for everything. You can enforce minimum password requirements. You can also add 2FA to any app now immediately.

I use Authentik as my identity provider: https://goauthentik.io/https://goauthentik.io/

There's good guides to settings it up with traefik so that you get let encrypt certificates and can use traefik for proxy authentication on web based apps like sonarr. There are many different authentication methods an app can choose to use and Authentik essentially supports everything.

https://youtu.be/CPURnYaW3Zk

SSO should really be the standard for self hosted apps because this way they don't have to worry about ensuring they have the latest security for user management etc. The app just allows a dedicated identity provider to worry about user management security so the app devs can focus on just the app.