Hi Kris,
A couple of months ago I got my hands very briefly on an RPi4 and tried out building Cinder with success. Here is a screenshot that I took back then of the Deferred sample running on device.
You basically need to 2 things as far as I remember for this to work. First would be to install the X dependencies ( along with the standard RPi3 dependencies ) which are not part of Cinder’s RPi guide currently:
sudo apt install libxrandr-dev \
libxinerama-dev \
libxi-dev
Second would be to use Cinder’s es3 GL target when building the library and/or samples:
cmake .. -DCINDER_TARGET_GL=es3
I believe these should be the only two things needed in order to get up and running on the default RPi4 setup.
Hope this helps,
Petros