I wish there was a simple guide somewhere to install Riot on a Rpi so that I could try it out.
Now if you mean to get your own local riot frontend for it, I thought there were some docker scripts that would let you do that quickly but I haven't tried those.
If you go to the trouble of working on multi-year open source project it shows a lack of foresight to not include a quick install guide for one of the mostly widely sold hobbyist hardware platforms in the world.
matrix-synapse does have quick install guides but a RPi is probably a bit too low spec to run a matrix server that will federate with matrix.org (though it depends strongly on what rooms you join and how many users you have).