PHP Fatal error: Declaration of Drupal\entity_reference_revisions\Normalizer\EntityReferenceRevisionItemNormalizer::normalize

I needed to update the method signature for the normaliser to allow the update to Drupal. Patch is attached for anyone that needs it.

How is that code loaded? Are you using some kind of devel or similar module?

As mentioned above, this service is not defined when using d10 and the class should not be loaded.

We extended this class in our custom code. Not sure if this is still needed and if we should just implement our own version.

Ok, if you actually use the hal module then you want to update your code and extend from the version in the hal module now. If you don't have hal enabled you should be able to safely remove this.

In our case, we just needed this for default_content integration, but v2 doesn't rely on this or the hal module.

Thanks, I'll create an issue on our backlog to update our code!