So I've been using Resilio to keep all my files (docs, art projects, music and video libraries and some random stuff) synced across all my devices.

This presented a problem with the Steam Deck, in that it requires substantial workarounds to make Resilio work (mostly due to how Steam keeps stuff locked down).

I solved this problem by avoiding it completely: started a virtual machine, ran Debian, and got Resilio working there no problem. 15ish hours later when all my files had synced, the final part of the problem needed solving: how to quickly move files to the host machine from the vm, and in the opposite direction on occasion.

Again, there were many fiddly methods, which I quickly dismissed as being too much work. Instead, my first attempt was to install Keet on both, which made it easy to move files, but it was one at a time.

What I finally settled on, was using Syncthing on both, and just having a folder I could dump stuff into. Can easily move things in both directions, and files move almost instantaneously since it's all essentially on-device.

Redundancy is preserved, can access what I need on the device I need it on, and I've worked around the limitations of the Steam Deck without any messy processes that could potentially break after an update.

Success!