

I use Authelia. I found it pretty easy to set up. They even provide guides with examples on how to integrate with other applications. For instance, I use Traefik for my reverse proxy: Traefik | Integration | Authelia
You can use a simple YAML file for your IdP or LDAP if you need more than a handful of users.
Even if you just take screenshots before making changes, this can really save you from an extended downtime while you try to retrace your steps after a failed configuration change. Screenshots take up very little space and can be moved to written documentation (even less space) or deleted (no space!) as needed. ShareX is a great FOSS tool for this.