How to handle migrations with multiple entity managers in DoctrineMigrationsBundle 3-CodePudding

On doctrine/doctrine-migrations-bundle 2.* this was relatively simple - use the --em option (and use ContainerAwareInterface to skip any migrations from a different em/connection).

Now (on doctrine/doctrine-migrations-bundle 3.2.2), it seems the --em option is ignored, and the default em/connection is always specified, meaning the migrations for the default em are applied to every database. Edit: As pointed out in comments - --em is not ignored, it's passed through directly, it's rather our ContainerAwareInterface approach that's no longer valid.

There is a lot of conflicting information on how to set this up, some suggesting it should "just work" (Symfony Docs) and other describing workarounds (Issue):

https://symfony.com/doc/current/doctrine/multiple_entity_managers.html https://github.com/doctrine/DoctrineMigrationsBundle/issues/38

How does one configure this new version (3) of doctrine/doctrine-migrations-bundle to apply migrations only to their matching entity/db?

Edit: I've included below our config previous to upgrading, which along with the ContainerAwareInterface connection filtering approach, allowed filtering migrations to run only against the appropriate entity manager.

Our existing "doctrine/doctrine-bundle": "1.12.8" config (shortened, but shows multiple entity managers):

doctrine:
    dbal:
        connections:
            default:
                charset: utf8mb4
                default_table_options:
                    charset: utf8mb4
                    collate: utf8mb4_unicode_ci
                driver: '