A very similar issue seems to have been addressed in sshguard 2.3 where "Failed publickey" logs with the key fingerprint at the end of the log line (as per Bionic's openssh 7.6 behavior) were not detected and therefore not blocked.
https://bitbucket.org/sshguard/sshguard/commits/cbf6332a3b21486136574e6968367f0bda293b5a
A very similar issue seems to have been addressed in sshguard 2.3 where "Failed publickey" logs with the key fingerprint at the end of the log line (as per Bionic's openssh 7.6 behavior) were not detected and therefore not blocked.
https:/ /bitbucket. org/sshguard/ sshguard/ commits/ cbf6332a3b21486 136574e6968367f 0bda293b5a