Migration path for IDENTIFIED BY PASSWORD 'password_hash' when removed in MySQL 8
We will need to perform additional checks, but a workaround we have found is to simply instead manually set "authentication_string" and "plugin" in "mysql.user" to the desired values, and then execute "flush privileges". That is, to keep using 'mysql_native_password'  and sha1(sha1(password)) that we know the hash is calculated as.

We then wouldn't be able to make use of the new default authentication plugin though. A quick check also says that caching_sha2_password (new default) doesn't have a stable authentication_string wrt password. Two users with the same password yielded different values so I'm assuming its implementation is more advanced in what input is used.