I have been struggling with this problem for a long time. This error is basically pissed me off because it took a few days to figure out a solution.

So, each time when I have been trying to launch a ‘Package Control’ in Sublime Text 3 it was giving me the next error: ‘No packages available for installation’. After searching on Google and trying a couple of things by myself I found very interesting problem: if I launched Sublime Text 3 through Terminal under root rights (“sudo /Applications/Sublime\ Text.app”) ‘Package Control’ worked perfectly. BUT if I launched it as every normal app in macOS through Launcher it gave an error “No packages available for installation”.

Many people have the same issue and nothing is helping. I have been in the same boat before I found this brilliant solution: https://github.com/wbond/package_control/issues/1302#issuecomment-352076439

For some macOS users, it is showing a bug with certificates and even manual installation of ‘Package Control’ is not helping.

The solution is to install a PRE-RELEASE version of ‘Package Control’ which you can find here – https://packagecontrol.io/prerelease/Package%20Control.sublime-package

For me, it worked perfectly.
Hopefully, this article will help you to fix your Sublime Text.