Currently it supports GLES3. "Mostly" untested. (In other words, it works just fine on a x86 Linux system with NVidia drivers...)
I am not sure about how the init context works. dpJudas would know more about that...
One thing you can try is using real OpenGL and seeing if it sticks. I would suggest using "-glversion 2 +gl_es false" on the command line to try this. It probably won't be accelerated - but if we're lucky, maybe your distro has a wrapper installed that might translate some parts of it to GLES2 for you. If not, at least it was worth a try.
Something not working in GZDoom that's not a bug? Is the display a bit quirky and unexpected? Post here.
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