RKE up fails with FATA[0341] error

When running $ rke up I get the following error FATA[0341] [ "{{ hostname }}" not found]
Can please someone help ?

Which OS do you use?

Thanks for your reply.

At this time I was using Ubuntu 18.04 which was outdated.

After an upgrade to 20.04 I did not have this incident anymore.

By the way, what does this error mean ?

Have you been getting this error notification regularly or just now?

As far as I recall, I got this error three times during a three months time span.