Per the core code being merged in https://core.trac.wordpress.org/changeset/59008, we need to modify the Enhanced Responsive Images plugin to ensure the relevant logic is only loaded if not already available in Core, for compatibility with the upcoming 6.7 release.

Maybe a good way would be to check for existence of the wp_sizes_attribute_includes_valid_auto() function?

We still have some time to do that, but good to have an issue already. We could get started on this at any point prior to the WP 6.7 release.