Allow editors to choose entity bundle when creating content through the "Entity form" plugin

Problem/Motivation

When using just the Inline Entity Form on a host entity, the decision on which bundle to use (on the entity creation form) is left to the end user, before opening the entity form:

Currently the Entity Browser widget "Entity form" forces the site builder to define a bundle in advance (and only one value):

In some cases (for instance when working with media entities where different bundles could co-exist in the same entity_reference field), it would be interesting to leave this option to the end user, and not restrict it to a given bundle.

Proposed resolution

Allow users to choose entity bundle when opening the form.