I had similar problem (no sshd accessible on 22 port on CoreELEC running from CF card). The reason is this:
journalctl -u sshd
…
Jan 01 00:00:25 CoreELEC ssh-keygen[3078]: ssh-keygen: generating new host keys: RSA Could not save your public key in /storage/.cache/ssh/ssh_host_rsa_key.Kp3BJI6nwD: No such file or directory
…
With absence of sshd on CoreELEC host, I’ve been able to login via ‘Web SSH Terminal’ (in addon/services/) which is accessible on port 11111 from web browser.
SOLUTION:
mkdir /storage/.cache/ssh
systemctl start sshd
That is it.