Dunno been a while with the RockPi4 but generally open an xterm glmark2-es2 and it runs.
Thats why I was asking if you where running a desktop as ‘Could not initialize canvas’ reminds me of errors of trying to run a graphical app without an xsession.
The drm version I think should be run from a VT otherwise run from an xterm. I have never run the drm version and just saw “hint: glmark2-drm needs to be run in a VT” and though ok run it in another VT Ctrl + Alt + F (2 to 6)
There some old stuff from when I had a RockPi4 and have a read through as to be honest it takes a month or 2 and I have forgot.