A DNS Proxy/Forwarder server? That’s where you would configure how your .internal domain resolves to IPs on your internal network. Machines inside the network make their DNS queries to that server, which either serves them from cache, or from the local mappings, for forwards them off to a public/ISP server.
Option 1, except for the cloud bit. My KeePass file is stored in a restricted shared folder on my home file server, and auto-syncs to my phone on the rare occasion I update it from my desktop.
I know nothing about any of the other alternatives mentioned here, but I’ll pitch in my 2 cents that I am very happy with OMV. Haven’t had to touch it since they day I set it up, maybe 2 years ago. Except one time when I wanted to add a new SSH/FTP account for someone.
In addition to the core file services, it supports running a Docker host, in which I have running instances of Portainer (a Docker Web UI), Transmission (a bittorrent client, woth VPN support, also with a Web UI), and Plex.
rsync, for sure. That’s what I used when I had to migrate a 10TB datastore to a new machins.