Yeah, can vouch for Owncloud (although I've moved to the NextCloud fork), its a convenient replacement for Dropbox, just thrown an OrangePi Zero ($7), a JMS567 USB 3.0 to Sata adapter ($3) and any old HDD and you've got yourself a libre Dropbox that uses just a few watts and works consistently on all platforms.
Note that the Wifi drivers aren't libre, but besides that everything else on the OrangePi Zero, from audio to ethernet is in kernel 4.10 under GPLv2.
Note that the Wifi drivers aren't libre, but besides that everything else on the OrangePi Zero, from audio to ethernet is in kernel 4.10 under GPLv2.