Thanks! I added the iptables rules according to your link. I had to use systemctl restart sshd.service instead of the command listed there. Still no connection.
I checked the correct IP with ip a.
sshd_config is large. I try to grasp all uncommented lines:
Code
PermitRootLogin yes
AllowUsers root
AuthorizedKeys File .ssh/authorized_keys
PermitEmptyPasswords no
KbdInteractiveAuthentication no
UsePAM yes
Subsystem sftp /usr/lib/ssh/sftp-server
Also, I wonder if SystemRescue is persisting changes for the next time I boot it up. When I logged in on the system itself with ssh localhost I had to accept the fingerprint again, although I already did this yesterday.