Now that's what I was looking for! Seems that libgbm is included with MESA, so building and installin latest MESA also builds and installs latest libgbm! Thanks!
But I need the sources for the latest libgbm1, not debian's install package for Buster. Do you know where those sources are?
Thanks, Dougie. I thought the ARM cores would have these states implemented anyway, since they are used in mobile setups, etc.