Ok, so here is the verdict:
The original 2.3.6 Beta1 build from https://github.com/sabnzbd/sabnzbd/releases
build runs perfectly on all my VMs from 10.9 through 10.14.
Test 5 however only runs on my 10.12, 10.13 and 10.14 VMs.
10.9.5 and 10.10.5 both tell me that the app bundle is damaged and can't be opened.
10.11.6 does however try to launch, but instantly crashes with this error message left in the crash log:
Dyld Error Message:
Symbol not found: _getentropy
Referenced from: /Volumes/VOLUME/SABnzbd.app/Contents/Frameworks/Python.framework/Versions/2.7/Python (which was built for Mac OS X 10.12)
Expected in: /usr/lib/libSystem.B.dylib
It all depends on what the official support plans are, if 10.9 through to 10.11 are dropped, then the new build is fine, if not, then more build testing is required.
I suspect HorseCalledHorse is running into hardware incompatibility with some instruction being used at compile time which isn't supported by his CPU, where as Test 5 is running into software incompatibility where the the build simply doesn't target anything older than 10.12.
Data from http://gs.statcounter.com/macos-version ... /worldwide
indicates that Mavericks (10.9) is barely used anymore:
As of November 2018
Mojave (10.14): 26.76%
High Sierra (10.13): 33.33%
Sierra (10.12): 14.92%
El Capitan (10.11): 11.94%
Yosemite (10.10): 7.45%
Mavericks (10.9: 2.46%
We could probably afford to drop 10.9, but 10.10 and 10.11 are still quite used.