I am running armbian buster Armbian_5.91_Rockpro64_Debian_buster_default_4.4.184_desktop.img.
I need rt_preempt in order to run linuxcnc.
I started with the 5.0.21.tar.gz kernel source from <https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/> and the rt_preempt patch 5.0.21-rt16.patch.gz from <https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/>. I applied the patch to the kernel source and compiled it on a 4gb RockPro64. It boots fine into a remote terminal using ssh but there is no display on my HDMI monitor. The white LED is showing but the red LED is not lit.
I had an earlier version of linux-5.0-rt running on armbian stretch so I mistakenly thought this would be a walk in the park.
Any ideas where to start looking?