Yeah I have had that problem, after doing an update because I have to change the config every time just to get it to display on my HDMI TV.
As I said in my other posts it should be in the FAQ that anyone who gets an "unsupported signal" for their display output should change the line in the config from
dtoverlay=vc4-kms-v3d,cma-256
To
dtoverlay=vc4-fkms-v3d,cma-256
Unless yours is the second one, then maybe try change it back to the first.
A couple of other things I had to change:
hdmi_group=1
hdmi_mode=16
hdmi_cvt=1920 1080 60 6 0 0 0
Hope this helps you or anyone else who has this problem.
