The order of steps seems wrong. The innodb modification to mysql server config needs to happen prior to database creation

[Peter Kahn]

This question is in reference to Atlassian Documentation: Connecting JIRA applications to MySQL

The articles states your should create the DB and then change your mysql settings.  doing this results in errors and you won't be able to attach JIRA to the DB.

I suggest you modify my.cnf prior to creating the DB.

[Peter Kahn]

Actually it is far worse.  JIRA supports mysql 5.6 not 5.7 and while it may be possible to downgrade to 5.6 on xenial, on mint sarah it was not.  Switching to a distro with 5.6