Quick explanation

I was just wondering what the difference is between the Raspbian distro in the Libre repository vs the ones for the raspberry pi?

Yes me=noob.
Thanks in advance.

We add board specific bootloader to the first 1MB of the image, install GRUB and our Linux kernel, sprinkle some optimizations for better performance, and remove some Raspberry Pi stuff.

There is not much difference due to the amount of upstream work thay has been done for the SoCs by our consultancies and the community. All of our boards share the same kernel.

Can I do this myself to try out diff distros? If so how to?

https://hamvoip.org/#download

Last time I checked, AllStar required an out of tree kernel module that requires Linux 5.16 or below. Since the driver is not upstream, you need to check with the driver author. We don’t have much insight into HAM at the moment so maybe the HAM community is a better resource than we can be.