All the kernels I’ve used are unpatched upstream kernels. I notice you mention above that you are maintaining some patches. Do you think those patches might have a bearing on this? If so I can try to build a kernel with your patches.
Oh upstream OLED won’t work and there is a known issue with the backlight. I am using this hack to make it work.
A cleaner solution would be this patch series which adds a new dtb for the OLED variant.