I think this is for setting the NS records with the registrar though? I could be mistaken - never have dealt with .is domains.
Since, as mentioned, this is stuff that is only important every few months, it's hard for me to have the discipline or motivation to properly look into it.
I get that. I currently manage 20+ domains with certbot so it would be a like weekly exercise, as somehow I manage to have them diverge on expiry over time, even when sometimes I try to re-cluster them to expire on the same date.
.isdomains.