We have a host running 10.1.43 with around 4k roles.
We did a full logical copy (using mydumper and myloader) to migrate all the data to a 10.4.13 host.
The import gave no errors, but all of a sudden we saw that the existing users with their assigned roles were not able to perform actions, they were getting permission denied.
Looks like the default_role is lost somehow on the migrations?
Doing a quick test over two hosts where we imported this into:
labsdb1009 -> 10.1
labsdb1011 -> 10.4
db1141 -> 10.4
Trying to isolate this a bit more
Looks like the default role gets lost after mysql_upgrade runs?
The work around for this seems to be: