Newly created field not being added to entity
You can't add this dependency, it's bundle configuration which you don't have and don't need in a bundleless entity. For testing better add a user instead of a node field or check the already pre-installed field.field.user.user.user_picture.yml
To create the field config you only need to specifiy the field storage and the bundle (for a bundleless entity this is the entity id). The other values are then extracted from the storage config:
$storage = $this-&gt;entityTypeManager-&gt;getStorage('field_storage_config')-&gt;create($field_storage_values);
$storage-&gt;save();

$field = $this-&gt;entityTypeManager-&gt;getStorage('field_config')-&gt;create([
  'field_storage' =&gt; $storage,
  'bundle' =&gt; 'my_entity_id',
]);
$field-&gt;save();

BTW part of the field UI is also the configuration of display modes. You need to add the new field as component at least to the default view and form mode, so that the new field is visible. See How to change the entity view display configuration programmatically?