That's what I have in config.txt, I'm surprise to see that we don't have exactly the same file. I have in addition some #Hdmi things, could I delete it?
[pi4]
# Enable DRM VC4 V3D driver on top of the dispmanx display stack
dtoverlay=vc4-fkms-v3d
max_framebuffers=2
#hdmi_enable_4kp60=1
hdmi_enable_4k=1
gpu_mem=256
max_framebuffer_width=3840
max_framebuffer_height=2160