Unfortunately, I had to stop developing SolydX RPi as an official version of SolydXK (announced on July 16, 2017. However, you can download a SolydX RPi3 64-bit Community Edition image for testing based on Debian Buster. Read the call for help on testing here: http://solydxk.com/solydx-rpi3-64-bit-testing-help-needed
You can still download the old versions here, but you do so at your own risk.
These images are a community effort. There is no official support for the SolydX RPi editions.