What unified login to use?

I'm setting up a server with nextcloud, plex, matrix and some other things I don't yet know, for some friends and family, (about 20 people if I get lucky)
and now I heard of a thing called single sign on/unified login. (Login to different services with the same user/pw and/or login once, access to all services)

so far I found out about Keycloak https://en.wikipedia.org/wiki/Keycloak

is this what I'm looking for? does anybody have experience in this? Are there other/better/simpler solutions for this?