Looking at your above screen snapshot, no sure whether you actually boot into the XFCE Desktop. You mentioned you managed to “boot normally”. What do you meant by “boot normally”. Did you managed to boot into XFCE and able to launch applications on the desktop?
I presume you are raising this you now cannot boot into the XFCE desktop. If your Manjaro XFCE image is not not able to boot up successfully, try another dtb. As suggested here:
The meson-g12b-am6-plus.dtb that you are using now might not be working for your Ugoos AM6 B Plus.
Or reflash Manjaro XFCE again.