This is a little update. As I continue writing software for D&D with the Dragons, Druids, and Dice project - I have created a dedicated web page for this project.
https://mrgibson.com/dragons-druids-n-dice.php
Here I'm sharing code, screen shots, executables.
My development for the C64 has be sparce as there are some pretty good development platforms for most systems, but not so much for the C64. For physical hardware, I'm using a "TheC64" and there is not another real way for me to write and test the software easily.
For the really old platforms, the TI-99 looks the best and mainly I understand development on it the most.
For Linux, Windows, and MacOS - I'm finding myself using tool sets that I have written before to perform many different types of tasks. Really, by far, Linux is the easiest platform to develop with.