Work in progress.
If you are having trouble getting a signal on your monitor/TV from a Raspberry Pi no matter the settings in boot/config.txt it might be because of the experimental GL driver.
No matter the settings in /boot/config.txt i always got to a signal during boot, but "no signal" when the desktop was supposed to show up, or the monitor detected the wrong resolution ([email protected]).
# uncomment to force a specific HDMI mode (this will force VGA)
hdmi_group=1
hdmi_mode=4
# uncomment to force a HDMI mode rather than DVI. This can make audio work in
# DMT (computer monitor) modes
hdmi_drive=2
The disappearing of the signal doe not have anything to do with the resolution settings at all, but was in fact caused by the experimental GL driver. Disabling it with raspi-config solved the problem.
Useful link: config.txt documentation