I remember getting pretty upset when Chrome shutdown the app launcher, this was a feature I used on quite a few sites.
Luckily thanks to work we have done for Android you can have it back now on your Discourse site.
chrome://flags/#enable-desktop-pwas , turn it on.
If you also want to capture links and send to the page enable
Desktop PWAs Link Capturing and there is also some extra caching you can turn on.
Then, visit your Discourse site and click “Install to desktop…”
You now have a dedicated application you can launch for your Discourse site.
On Chrome on Mac the terminology is a bit different, but it works nonetheless.
It is important to note that this will not work with for you on all sites, you need a manifest and some fancy to support it.
Note This is definitely a big Electron killer for simple repackages given that it is stuck on Chrome 59 now.