Fancy! What toolchain/compiler do you use for the Dreamcast? Is there an open one with documentation?
I'm using https://github.com/KallistiOS/KallistiOS which is a FOSS reimplementation of the dreamcast SDK, paired with https://github.com/Kazade/GLdc which is a performant opengl implementation (but incomplete and with a few bugs). So I get to use opengl1.2 for console dev which is pretty great!
There's documentation for most of this (though a lot of it is out of date) and KallistiOS even comes with a script to automate 99% of building the cross-compilation toolchain.