Weird about Syncthing, it works for me on Windows, Mac, Linux, and Android. But I find file permissions difficult so that could be it.

It's nice for my use case: I tend to download things on my phone but I often want them stored permanently on my computer, so I just dump them in a Syncthing folder and It takes care of the transfer automatically. Once it's on my computer my backup program (Backblaze) will back it up too. But not everyone has that particular use case so it's not for everyone.