Sshd -t responds with unable to load host key even though host key exists

Are the permissions on /etc/ssh/ssh_host_rsa_key correct? It probably needs to be 600

What is the error when they are all commented out?

Also, are you running sshd -t as root? Because you won’t have access as a normal user.

Lastly, have you tried starting it with systemd instead? systemctl start sshd