I was able to install and runs EDK2 but not sure if it is reliable, there some strange side effects.
see Enabling DeviceTree on Pi 4 4 GB causes boot to fail, it hangs at dracut.initqueue
U-boot is still in my agenda, as soon as I can spare time. Currently setting up my home automation on raspberry pi is + docker (and eventually I can close and open my blinds 
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I checked once FCOS for the config.txt. As far as I remember, it doesn’t existed (can you confirm?), so I can’t do as said there
Activate UART0/1 with the following overlay configuration in
/boot/efi/config.txt: