"Setting up distributed builds": potentially add warning when ssh-ing to root user?

Observations
I was following along with the guide at https://nix.dev/tutorials/nixos/distributed-builds-setup.html , and I was stuck at the part asking me to run

nixos-rebuild switch --no-flake --target-host root@remotemachine

Problem
I was running into an error produced by ssh:

root@localhost: Permission denied (publickey)

Approaches
This was because I had the sshd option PermitRootLogin set to no, as per common security practice. Others may be running into this issue and have forgotten that they have this option set: it might be helpful to add a small reminder around there to have one check their options if they can't run the rebuild.

Willing to help?
I wouldn't mind!

Priorities

Add 👍 to issues you find important.

Start with the distributed builds setup guide at https://nix.dev/tutorials/nixos/distributed-builds-setup.html, especially the command using --target-host root@remotemachine. Check how the guide currently introduces SSH requirements, then add a reminder to check PermitRootLogin when SSH reports public-key denial. Done means the warning appears at the relevant step and explains the reported failure.