I recently couldn’t install Insync manually because of a deb dependency. I use debs to install and I also use the Mate so I want the insync-caja deb package installed too. The insync-caja package has a dependancy to the deb insync-emblems-icons package. As far as I can tell, there is no place to download that package manually from the insynchq webpage. Yes, you can get it from the apt repos, but that only works if you have the insync repos working. People have had issues with the repos in the past, so I can’t say they are all that reliable. This typically happens when a new distro release happens:
Also, some system admins run a private apt repo, having it directly downloadable is much preferred to trying to scrape it out of a repo.
TL;DR version - Add links to the insync-emblem-icons packages in reasonable places so admins can download them.