Operating rpi4 with rspbian buster without monitor plugged in ('headless') using remote access e.g. VNC or Anydesk I get a poor resolution of 640x480 (or so). When a full-hd monitor is plugged in before reboot, the remote resolution is also full-hd.
During normal operation there is no monitor plugged in. Using raspi-config -> advance settings -> Resolution, set to DMT Mode 82 1920x1080 60Hz 16:9 did not change this at all.
found no suitable help here and in other forums. Was no Problem earlier with RPi3. Any help what has to be configured?