This module is great, and we are using it across several sites now. While the content types are relatively similar, most of the sites have several fields that aren't used across all sites. There's not really much of a reason for us to see notices whenever an unknown field is encountered by the client server. This patch just comments out that one line that generates the notices.
Active
4.0
Entity Share Client
Nothing too fancy, but maybe this will be useful for others.
The right way to do this would be to add a new import processor, which runs in the STAGE_PREPARE_IMPORTABLE_ENTITY_DATA stage, and removes the data for the specified fields from the incoming JSONAPI.