As said I took the sources as above and used it only internally for my build. I use github only for one device yet and there will be not much more in the future since I’m not a developer.
You need to download the device, kernel, vendor and hardware files and put in your build environment. Then you can build with docker or the repo way.
Porting Postmarket for a new device is a very big effort (compared to my IT skills) that i tried a few years ago for the Galaxy s4mini, and was not abble to achieve, (the Galaxy Tab 2 was already ported by another guy, and it is now a community supported device…)