I’m using Authentik at home and at work. It’s a fairly complex, and extensive, tool. Aside from some of the user login flows being tricky to get my head around (logging into Authentik, not integrating with the other apps), it’s been a great solution. I have done proxy auth, OIDC, and SAML. I haven’t needed to dive into LDAP yet.

I personally use Authelia. I find the installation no be easy and lightweight.

I originally switched to Authelia from Authentik because I wanted to authenticate Radicale. Authentik had more features including a beautiful admin page, but couldn’t proxy HTTP basic authentication, which is required for Cal/CardDav.

I have since switched Radicale to Nextcloud, so may consider switching back to Authentik.

One important thing to note about Authelia is that a single instance can only authenticate for a single domain, so your installation will require at least two instances if you go with Authelia. I am not sure about Authentik.

Overall, SSO is great and I would highly recommend you use it for your services. You can find Authentik tutorials here: https://goauthentik.io/integrations/