Hello friends.
I also successfully booted with nvme without uSD and mmc.
Used the image: Armbian_19.11.3_Rockpi-4b_buster_legacy_4.4.198
Hardware: RockPI4B + KingSpec SSD M2 nvme 120gb
First updated SPI flash via rockpi4b_upgrade_bootloader.sh
U-Boot 2017.09-2681-geb41d9a6ce (Nov 04 2019 - 09:32:53 +0000), Build: jenkins-linux-build-testing-2-85
Also in arbianEnv.txt added fdtfile = rk3399-rockpi4b.dtb
and copied rk3399-rockpi4b.dtb to / boot / dtb