Haha, everything was fine with kernel 5.5 and modified tools.So, updated to kernel 5.5.8 in 15.1.3.47255 and the tools built automatically, although it did some funky things like a larger than normal cursor and other video-related abnormalities.
Made the changes to the two Makefiles for prl_fs and prl_vid per above and everything is copacetic again... Cheers, again @Devries!