TechnicallyUnsure

Download Debian BullsEye CLI for Rock 5A from here:
https://www.okdo.com/software-hub/

Burn that into SD Card and boot the Rock 5A / Rock 5A Pink
 
Log into the CLI from the console itself, using mouse and keyboard, or SSH into the Debian

then run these two commands:
apt install ssh ntp
sudo ln -s /lib/systemd/system/ssh.service /etc/systemd/system/sshd.service