Sonata Admin 3 only supports Symfony 4.4. Upgrade to the latest Sonata 4
versions still compatible with Symfony 4.4 / PHP 7.4 (admin 4.22,
doctrine-orm-admin 4.9, media 4.6, classification 4.3, block 4.19,
formatter 5.0, translation 3.1), which requires DoctrineBundle 2.7,
ORM 2.14 and doctrine/common 3. DBAL is kept on 2.13 for now.

Bundles incompatible with DoctrineBundle 2 or Sonata 4 are replaced:
- specshaper/gdpr-bundle: the prestataire IBAN uses a new
  encrypted_text Doctrine type (same algorithm and key). A reversible
  migration unwraps the stored values from the GDPR serialized object;
  the 33 existing IBAN are checked to decrypt identically.
- prodigious/sonata-menu-bundle and pixassociates/sortable-behavior-
  bundle: their code is copied in the application (MIT), keeping the
  same tables and admin codes (roles stored in database).
- Unused bundles removed: doctrine-encrypt, JMS serializer, knp
  markdown, roromix spreadsheet, doctrine cache, easy extends.

Admins, CRUD controllers, the security handler, the export data
sources and the templates are adapted to Sonata 4 without behavior
change; the admin layout now extends Sonata's one and only overrides
the Kohinos blocks. Migrations handle the Sonata Media/Classification 4
schema changes and the renamed gallery item roles.

The smoke baseline only changes for removed pages (/gdpr, public media
galleries, CKEditor browser URL) and admin AJAX/search URLs called
without parameters. See doc/migration-symfony8.md.