Did both. Setting up your own VPN is a bit annoying but when it works it works. Tailscale is really easy and solid. For folder syncing I can recommend using tailscale and syncthing. Install both on both devices, then connect the devices in sync thing (it will reciprocate) and then you can add a folder and share it with the other device. Latency for syncing can be 10s-3min, plus the actual file transfer speed.

Knowledge level: configuring software and setting up software. Maybe some basic network troubleshooting if it comes up.

It’s never gonna be as easy as paying for a service that does it for you but this setup is also not that hard.

If you have questions feel free to ask me or other nerds on here, I’m sure they can help you ^^~

Not a Linux nerd but just to make sure you checked the basics: did you verify integrity of the OS image? Are you able to verify your USB, memory and HDD all work in isolation?

My first hunch on this is hardware issue, because you get hard shutdowns from what I can gather. I could be wrong though, I only install OS occasionally.

He looks very polite. Like he will stroll through your garden but respect the privacy of your flowers.