If you want to keep your filesystem in sync across many devices Syncthing fully enables this.
It is a use case where you would expect a payed service would be easier or more reliable but with Syncthing it is the exact opposite. Just install it on your devices and select the folders you want to keep in sync ... done.
I had never had any problems with it something I cannot say about Dropbox which can be terribly slow, hogs my PC and resulted in lost files on some occasion.
My filesystem consists of [checks du -h . | tail -1] 189 GB.
I don't think Syncthing (which I love) can cram 189 GB on my 64 GB phone.
Yet I expect to have access to my filesystem from my phone.
Synthing is a nice "pump-hose system" between reservoirs of data. What I was arguing above is to stop having separate reservoirs of data to begin with.
The issue is not so much "can I browse a virtual file system" but more "why should I depend on one local file system sitting on a remote server, probably owned by a third party, as being the single source of truth for my own files."
I use syncthing. It's awesome for computers. Coming from Dropbox, then Nextcloud, I find it solves all my needs much, much better, at least on well-supported platforms.
I love how I can decide what to sync where, and even create my own topology of sync-devices if I like. That may sound like crazy complex stuff and over-engineering and what not, but it was a solution I landed on organically, just through normal use.
That said, it's not entirely smooth on iOS and you sometimes needs to manually launch the (third party) app to force a sync after changing some files.
Syncthing doesn't solve the problem OP is talking about. It's amazing software that works as long as you don't have to sync the same file edited on two machines before they have a chance to sync. There is no logic, besides something using CRDTs, that can reliably resolve the conflicts in every situation when you just have two sets of bytes and nothing else.
Even if you maintain "last synced" copies + the current latest version and use those to compare against the server there are still simple situations where the conflict resolution doesn't work and/or requires user input. Anything that requires user-input like that can't properly sync binary files without resorting to making a new "File (Conflicted 1).sqlite" which you now manually need to compare.
I just wish Syncthing would allow for deferred sync, i.e. you see the file, but it only gets fetched once you access it.
That's, imo, the only way to sync large folders. I don't need all my Documents/Photos/Movies/Whatever on my phone at all times, but I do wish I could access them when I need them.
