[U-Boot] Rpi4 u-boot

Hello, I am hoping please for some assistance getting u-boot to run on a Rpi4. I had downloaded the image contained at : https://download.opensuse.org/repositories/home:/mbrugger:/branches:/RPi4/op... And dd that to my SD card. This runs fine, but there is no uEnv.txt and even when I added one, it still went to the Suse GRUB. I note that when I tried to compile u-boot 2019 v10 it seemed to compile ok, but no dtb files where generated? If I copied just the uboot.bin file there is no output on my serial port to indicate that it is working? And again without the ability to make any changes via uEnv.txt I am a bit stuck.

Any help would be much appreciated.

Thanks

Al