Yeah it might clean the sources, but if you do not clean the debs with it and they are already present in the output directory the clean flag is worth nothing
You did not ask for it
Just kidding, glad you could figure it out.
Anyway, we cannot provide each kernel branch in each flavor for each board. Would simply be way too much images to build and data to move around. However you always have the option to use the build script to build any flavor with any kernel branch available for your board.
You're welcome.
If you need to know in which ways Armbian differs to "vanilla" Debian or Ubuntu just take a look at the build script on Github: https://github.com/armbian/build
There - besides of the kernel sources and patches - you will find bsp packages and tweaks which are included or applied to each board individually depending on their family. For examples optimizations to increase sd cards lifetime or power consumtion.
Probably noone really tried to do such a thing . If you think about the boards price tag it is simply not worth wasting time to do emulation for testing.
If another community member has experience with this and is willing to help it is more than welcome. However from Armbians side there is probably noone that will take a look into due to general lack of ressources.
I dont know the specific reason for emulation to play with it beforehand but in general said Armbian is a Ubuntu or Debian OS, mostly unaltered, with a kernel package that will make it work on a particular board.
From userspace point of view there is little to know difference from having Debian as Armbian on a Board or Debian as - well - Debian ^^ on a PC or virtual machine. Binaries need to be armhf/arm64 or x86/amd64 of course but that's it. So maybe you can test whatever you wanna make run on your board with a x86 virtual machine as well.
If there are not specific reasons to use 5.8 you can stick with 4.4. @NicoD explained in a video why this is a good idea depending on your needs:https://www.youtube.com/watch?v=NLY5nbMaT6U
There is a Debian image available.
If you want Buster with 5.8 kernel you need to build that on your own. Build tools will help you to do this: https://github.com/armbian/build
Install compiler and compile your source code? Hard to tell what is needed without any info whatsoever about your program