How to configure MySQL 8.0.21 to use databases from 8.0.18 on macOS 10.14

I upgraded MYSQL 8.0.18 to 8.0.21, on my Mac Mojave, using the release mysql-8.0.21-macos10.15-x86_64, which Oracle says supports Mojave 10.14…

Now I can’t get MySQL to access the databases created under the previous version. I’ve tried all that I could find:

stop mysql server

a) copying (cp -aR ) the /usr/local/mysql-8.0.18-macos10.14-x86_64/data directory to mysql-8.0.21-macos10.15-x86_64. Start server. Results in the mysql server NOT starting… (yes, permissions, ownership, and structure are exactly what they need to be).

or

b) selectively copying (cp -aR) only the database directories and ibdata1 file from …old../data across to …new../data . Start server. MySQL starts, but my "old" databases are not available.

Any help with this would be appreciated. I ‘m stuck. I believe this is possible, I perhaps need to copy just the right files over to the new directory…