The first few ROS tutorial pieces have gone well. I'm getting a feel for catkin (the build manager within ROS). Reminds me of PHP's artisan manager for Laravel.

I've gotten to the point in the tutorials where apparently I will need some manner of Xwin GUI. Ubuntu Mate seems to be the favorite, but no version for Pi 4. Tempted to go with the familiar Kubuntu KDE but that's a lot of overhead. More research required...