@Righto123 What I do know is that Dreamcast requires "OpenGL> = 3.1 GPU" to work on the PC:
https://github.com/recalbox/recalbox-os/wiki/Board-Compatibility-(EN)

None of the Dreamcast games are running on the PC, or just Marvel vs. Capcom 2?

If none works, it is the video card that does not support, if it is just one game, try changing the emulator / core.