Problem/Motivation
The EntityReferenceAutocompleteWidget will always return a maximum of 10 results, which is caused by the call $entity_labels = $handler->getReferenceableEntities($string, $match_operator, 10); in Drupal\Core\Entity\EntityAutocompleteMatcher::getMatches().
Proposed resolution
Make the match size limit configurable as is the case with the operator.
Remaining tasks
None.
User interface changes
New "Number of results" setting on entity reference autocomplete widgets. Defaults to 10.
API changes
N/A
Data model changes
match_limit setting added to entity reference autocomplete/tags field widget config schema.