I do not have a Steam Deck but I do use Linux.

Doesn’t it have a Micro SD card slot? That would probably be the least faffing way to copy files.

Aside from that it’s just a Linux computer so anything you like; I’m partial to SSH (rsync) for one off or Syncthing to sync folders around. You could also use a magic-wormhole web client, a Windows shared folder (no experience connecting to SMB shares from Linux), or croc (like Magic wormhole but resumable).

Also not a user of pirated game files, but what kind of format are they? If they are EXE files then they won’t work when you double click them like on Windows (at least not unless SteamOS went to the effort to configure that). You have to run them with Proton from Steam. I do not know how to do this with things outside Steam but you cauld try adding them to Steam as an external game, then the usual “select Proton” configuration might present itself.

The .org is down for me but .si isn’t. It wouldn’t surprise me if the Spotify download triggered some legal proceedings and resulted in a DNS name being blocked.

HexOS(TrueNAS) + Headscale(Tailscale). Then Emby or whatever existing tool on it.

TrueNAS supports cloud backups on a schedule to Backblaze; easy to setup, failure alerts. Then with Syncthing or the like you can have a 2nd copy of data on another computer.

I keep anything of importance replicated to most of my devices all the time (photographs are on laptop, server, phone, documents on all three and a media machine encrypted with version history). Then the server does snapshots for easy data recovery back in time, and a cloud backup nightly to Backblaze for off-site-ness.

HexOS is not cheap, but it’s a nice wrapper around TrueNAS. It supports a simple interface for just enough to cover most simple use cases. Then you can drop into TrueNAS if you want something more advanced.

Though I would love to help, I’m no better with a list of unfinished projects :| I could help setup something over a call at one point but I am probably not a good person to keep you accountable.

I use TrueNAS (HexOS) to host Immich (Google Photos), Paperless NGX (Google Drive sort of), Headscale (Tailscale VPN), Syncthing file sync, Backblaze cloud backups, Emby, etc.

I would recommend Emby over JellyFin personally. I have used Plex, JellyFin, and Emby. Plex is removing the point of using it, JellyFin seemed constantly broken for me. Emby worked the first time, and has continued to work without issue since.