Retrotrigger you cannot load the gamecube with your card, it is OpenGL version string: 2.1, version 3 is required.
leo_kendall the file glxinfo.txt is empty in your targz, i don't know why, but according to your error, i guess that's the same issue.
For each computer :
DISPLAY=:0.0 glxinfo | grep "OpenGL version string"
will give your the opengl version supported.
for dreamcast, version 3.1 is required. for gamecube/wii, it is at least 3.0 i think.
i will display it in the next release in the menu.