It sounds like your Raspberry Pi 4 and 5 are having trouble reading the EDID (Extended Display Identification Data) information from your monitor.
First step remove all boot media (sd or usb) from the Raspberry Pi 4 and power it up while plugged into your monitor. It will power up into a diagnostic screen. Look for the line that starts with "display:" and it should tell have something like edid=ok
https://www.raspberrypi.com/documentati ... iagnostics
Next, I don't use Ubuntu, so I can't tell you exactly where this will be. On Rasberry Pi OS you can edit /boot/firmware/cmdline.txt and add the display resolution to the line. Don't create a new line or your Raspberry Pi may not boot!
The following post gives the details.
viewtopic.php?p=2115124#p2115124
First step remove all boot media (sd or usb) from the Raspberry Pi 4 and power it up while plugged into your monitor. It will power up into a diagnostic screen. Look for the line that starts with "display:" and it should tell have something like edid=ok
https://www.raspberrypi.com/documentati ... iagnostics
Next, I don't use Ubuntu, so I can't tell you exactly where this will be. On Rasberry Pi OS you can edit /boot/firmware/cmdline.txt and add the display resolution to the line. Don't create a new line or your Raspberry Pi may not boot!
The following post gives the details.
viewtopic.php?p=2115124#p2115124
Statistics: Posted by AndyD — Fri Jan 10, 2025 5:45 am