It does very much need a cheap development board. Also, I might be blind, but while there are some references to the cores being 64bit, it doesn't seem to spec

It does very much need a cheap development board. Also, I might be blind, but while there are some references to the cores being 64bit, it doesn't seem to specify what ISA extensions they support exactly, anywhere in the pdf. I am thus going to assume the absolutely minimum RV64E.