Thanks for filing this bug in Ubuntu.
I believe you used an older version of the new installer, which had a known bug where the universe component was not enabled in /etc/apt/sources.list:
https://bugs.launchpad.net/subiquity/+bug/1783129
Please check your sources.list and enable universe (and multiverse if you want), then you will find the krb5-user package.
Thanks for filing this bug in Ubuntu.
I believe you used an older version of the new installer, which had a known bug where the universe component was not enabled in /etc/apt/ sources. list:
https:/ /bugs.launchpad .net/subiquity/ +bug/1783129
Please check your sources.list and enable universe (and multiverse if you want), then you will find the krb5-user package.