Mir

Comment 0 for bug 1667645

$ bin/miral-desktop
...
terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<std::runtime_error> >'
  what(): surface_after: surface is not a member of this session
Aborted (core dumped)

Using tiling WM doesn't exhibit this problem:

$ bin/miral-desktop --window-manager tiling

I would guess this is something to do with the recent addition of wallpaper. And possibly due to this test box being slow (14 years old), not due to Xenial/Mir 21.0.