I’ve just made a new SD card with latest Gnome for “RASPBERRY PI 4B/400/3B+/3B/ZERO 2”.
It can not boot - it shows a prompt and then goes to the screen where the power is turning off: https://photos.app.goo.gl/km87sBfLwAMipn7f7
No clue what the problem was before, could be any number of things. This image now is built on the unstable branch and kernel that is 7 months newer. Also there is a updated config.txt.
For some reason looks like your screen is not scaling. Guess you need a higher screen resolution than what was detected as default from the monitor’s EDID info. Can you go into gnome’s settings and change it some how.
Another thought is enable in /boot/config.txt disable_fw_kms_setup=1 and see what that does.
I also tried other screen settings, but it seems 800 x 480 is the limit of the official 7" display and the installer just can not do it for some styling reasons. It was not an issue with the Xfce installation time ago.
Maybe the minimum size of the installer has changed. It might be after going through the Install process and shutdown. Then hook it up to your smaller screen and boot up then set to 800x480 and see if it works.