You can by enabling global discovery and relaying in Syncthing. I am not that versed in this, as I only sync when I connect to my home wifi, which works so well for me. Do a search on it, lots of people have it setup for outside network as well.

I prefer not to use any ‘cloud’ computing. Even the idea of having your private info sitting on someone else’s server, gives me the willies. Use Syncthing, available on all devices, uses your own lan/wifi to connect and sync all your info. You can choose whatever storage option or redundancy you like. Keep your info in-house.

If you want gaming, check out POP OS (ubuntu/debian,) Garuda Linux KDE Gaming Edition (Arch) or CachyOS (Arch.)