I got the same error "could not initialize canvas". After I made sure I was using Wayland the benchmark worked fine (like eshelton wrote: " I also installed the ubuntu-desktop package to switch over to Wayland. On my first login, "echo $XDG_SESSION_TYPE" reported x11. I logged back out, and logged in again checking the gear icon to make sure the Wayland-related one was selected. I don't know if the gear icon was needed, but that time Wayland was active.").