Gwolf2u

I guess this should do:

for now I've stopped kernel upgrades
sudo apt-mark hold linux-image-current-rockchip64 linux-dtb-current-rockchip64 linux-u-boot-rockpi-4b-current can resume with
sudo apt-mark unhold linux-image-current-rockchip64 linux-dtb-current-rockchip64 linux-u-boot-rockpi-4b-current  
did this since the option to disable armbian kernel upgrades in armbian-config is not working in my case for some reason

I can't tell you how aggravating it is to read this, since this is the second time in three months that my Rock 4A has stopped booting after a kernel upgrade. I disabled kernel upgrades in armbian-config the last time it happened, but clearly that wasn't sufficient.
 
What's especially annoying is that in order to fix this, I have to take apart my whole device and disconnect my NVMe connection in order to boot from an SD card instead of the onboard eMMC.
 
I appreciate you pointing out how to stay on a specific kernel version using apt instead of relying on Armbian, since the latter is obviously unreliable. I'm likely to move to an x86 device in the not-too-distant future though, given occurrences like this, plus the lackluster support from the board vendor.
 

for now I've stopped kernel upgrades
sudo apt-mark hold linux-image-current-rockchip64 linux-dtb-current-rockchip64 linux-u-boot-rockpi-4b-current can resume with
sudo apt-mark unhold linux-image-current-rockchip64 linux-dtb-current-rockchip64 linux-u-boot-rockpi-4b-current  
did this since the option to disable armbian kernel upgrades in armbian-config is not working in my case for some reason