A few years ago I switched from Dropbox to Sync for its better plans and security. At that time they said Linux support would be coming at some point. It's been a PITA dealing with Sync's web access only. So I asked them if they plan to have Linux support any time soon, and this is their response:
With this disrespectful attitude I switched to Mega, Which DOES support Linux. Bye, bye Sync.Work on a Linux app keeps getting pushed back. Overall, the number of people requesting Linux has been relatively low. Linux is a passionate community and we're part of that community, however, we haven't been able to justify the development time and additional support overhead required to deliver a great Sync experience on Linux. Also being considered is the market segment which is relatively small.
We're not saying never on Linux, but we've been growing fast without it which is why it keeps getting pushed back.
So like we mentioned previously, it's on our long-term roadmap, but no ETA.
Sorry, we couldn't be of more help on this.