I also have observed this problem on bionic for several different computers. The workaround always solves the problem; without the workaround I cannot log in. What the computers had in common:
* Using bionic (either the version from the DVD or with network updates)
* Using networkd rather than NetworkManager with a static ipv4 address
* sssd.conf uses fqdn to refer to the name servers
* A backup ldap and kerberos server were both provided.
I also have observed this problem on bionic for several different computers. The workaround always solves the problem; without the workaround I cannot log in. What the computers had in common:
* Using bionic (either the version from the DVD or with network updates)
* Using networkd rather than NetworkManager with a static ipv4 address
* sssd.conf uses fqdn to refer to the name servers
* A backup ldap and kerberos server were both provided.