As others have said, Nextcloud for files/calendar and Tailscale for VPN is your answer.
Nextcloud can be installed in several ways, one of which is Docker Compose. Docker Compose is flexible but requires learning a bit, although you can use it for most self-hosted software.
I love XCOM and have tried a few of those games. Into the Breach is one of my all-time favorites. It captures the thoughtful, turn-based decision-making of XCOM but admittedly lacks the base building, graphics, and most of the leveling up, to name a few things.