I followed the guides around here and successfully installed Big Sur on my E6430 (i7-3350M, 1600x900) with OpenCore.
I got the OC config from here,
The only thing not working is the HDMI and output to second monitor. When I plugged in the HDMI cable nothing is happening, and if I press the Fn+F8, beep sounds comes and nothing.
I installed Mojave earlier and in Mojave I was able to update the Framebuffercapri and replaced it in Library/System/Extensions, HDMI was working back there. I have the updated Capri.kext file as well. but in big sur it is not allowing me to write to System read only filesystem.
How do I enable HDMI to work?