this single fact made it awesome for homebrew development, is how i really got started. burning a track on cdr to test each build forced some discipline before finally getting serial cable. while the dreamcast has a sh4, the vmus had arm chips, so if you wanted to do everything you had to have two cross compile toolchains. i remember it taking days on my athelon at the time.

the defacto sdk back then was kallistiOS

http://gamedev.allusion.net/softprj/kos/

The homebrew scene for dreamcast is impressive and still surprisingly active.

Good list of emulators available for the DC too, though in various states of functionality: https://dcemulation.org/index.php?title=Emulators