ok so "sudo mir_demo_server --platform-graphics-lib /usr/lib/x86_64-linux-gnu/mir/server-platform/graphics-mesa-kms.so.4 --vt 1" works
ok so "sudo mir_demo_server --platform- graphics- lib /usr/lib/ x86_64- linux-gnu/ mir/server- platform/ graphics- mesa-kms. so.4 --vt 1"
works