Hi @crustulumtheone,
at first, I also struggled setting up ssh autologin. I am a linux beginner, too. Our goals seems similar. I want to rsync my datadir to a remote raspi and beeing able to restore it afterwards (which I still struggle on).
For me, these two pages helped me set the ssh problem up properly:
Set up ssh autologin
https://www.shellhacks.com/ssh-login-without-password/
ssh-add error message
https://stackoverflow.com/questions/17846529/could-not-open-a-connection-to-your-authentication-agent
For me, the command eval $(ssh-agent) helped.
Cheers