Resolved! platform 5a001000.display-controller: deferred probe pending - Why did the UART output stop?
I compiled the linux kernel uImage and corresponding .dtb file with CubeIDE.Then I mounted the st-image-bootfs-openstlinux-weston-stm32mp1.ext4 and changed the extlinux.conf inside the folder /bootfs/mmc0_extlinux to # Generic Distro Configuration...