If you have a nas, I highly recommend you set up a VPN back to your network. It's been a bit of a game changer for me. I don't fiddle around with Dropbox or gdrive anymore, it's just on my nas and it just works. I was even mounting /home from it but that was a bit of overkill and still caused some hassles when I was completely offline- like on an airplane. Vpn has other advantages as well like no longer really having to worry about sketchy wifi networks. It felt annoying and like overkill at first, but I'm never going back to relying on any sync apps again.