A real case that just happened to my colleague:
He copied this as a command, figured he needs sudo, so he added sudo to the beginning, but didn’t notice it also needs to be added after the &&. This resulted in not adding the ros2-apt-source, which, when you continue with the sudo rm commands, yields a broken system. Interestingly, the rm commands have sudo.
@claraberendsen could you please convert all these commands in the initial post to actual working commands with sudo? (also, the cited command needs a # before the comment).