This could be in some cases a little bit problematic. We don’t provide SDK and it has several reasons.
In turris-build repository, you will find in README documentation what you need to do to compile packages with dependencies, which you need to have installed and also you might find there is workflow. There’s a possibility to use OpenWrt SDK, which I don’t recommend. One reason was said here a few days ago. Somebody downloaded outdated SDK and tried to compile something, which has a dependency for OpenSSL, but in that SDK was outdated and on his router, it was running the latest one due to fixes for security vulnerabilities. Another reason is that we are using patches and we could have the latest versions of some packages, which we sent to upstream (takes time to review it and merge it), but it was not included in the SDK. For the stable versions, they build SDK once a new version is released.
If I am not mistaken, there are 3 commands what you need to have working tools to compile packages for Turris OS / OpenWrt (git clone, cd, compile_pkgs script). It depends on your PC, but usually, it takes less than an hour. In my case, I have it ready within 20-30 minutes.
Package freeradius2-mod-files is indeed not available. You were using Turris OS 3.x don’t you? Freeradius 2 is deprecated and end of life. I was able to found this commit:
Freeradius2 was not available to install in OpenWrt 18.06 (and Turris OS 4.0 was based on top of it). I would highly encourage you to use Freeradius3. See their homepage:
I am not able to find luci-app-radius in Turris OS 3.x and not even in OpenWrt feeds. Isn’t there a possibility that you compile it and installed it yourself?
Regarding the commit, which you found in turris-os-packages it is not used and the branch should be deleted. We are using test(for 3.x), master (5.0.x/5.1.x), develop (5.0/5.1/5.2).