At the risk of going off-topic, my impression is that user choice takes a slightly different form on Reform. Instead of lots of different flavours of essentially the same thing (linux distros) the focus seems to be a smaller number of niche operating systems.
Obviously it comes with factory installed linux because that is the mainstream system that most of us will be familiar with and can get up and running straight away. For those more adventurous there are off-the-peg images available for 9Front and Genode/Sculpt.
A more complete list of different operating systems on Reform (including linux flavours) is here.