I have a Raspberry Pi 4 running Debian 11 (bullseye), however, it doesn't boot when a monitor is not connected. When the monitor is connected, it boots perfectly, however without it it stalls forever while booting. When it does this, I can't ssh or connect to it remotely.
The /var/log/messages says:
Dec 27 23:15:07 debian-pi kernel: [ 20.451738] vc4-drm gpu: [drm] Cannot find any crtc or sizes Dec 27 23:15:17 debian-pi kernel: [ 30.855155] Console: switching to colour frame buffer device 240x67 Dec 27 23:15:18 debian-pi kernel: [ 30.955513] vc4-drm gpu: [drm] fb0: vc4drmfb frame buffer device Dec 27 23:16:15 debian-pi kernel: [ 52.129976] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
after booting without monitor