Is it possible to sync a user to a self-hosted service that doesn't support SSO or federated authentication?

[GreatestFool]

Sorry if it's answered somewhere else. I wasn't able to find any, but it may just be me not knowing what to search for; I'm quite new to this.

Essentially, what I'm asking about, is if it's possible to sync a user (the username and password) when it's created and updated, to a self-hosted service? For example Jellyfin (I can't think of anything else, I know it has plugins for this). Would it be possible to use custom code to sync the password and/or username changes to an application using its API or something? I imagine it may have some security considerations, however, hence why I'm asking first.

Please do ask me to clarify if I'm being unclear, and I'll do my best to explain further.