Patch #14 adds the ability to mark the "redirect_source/path" property as unique in order to avoid duplication warnings.
Patch #2 didn't work for me with the latest version of Feeds. I have changed the namespace and added the option to set the "redirect_source/path" property as unique in order to avoid duplication warnings.
I can't reproduce the issue with Drupal 10.1.7 and Linked field 8.x-1.5. It's working for me.
I have modified the patch to make it compatible with 2.0.0. The patch #2 was generated from the branch 8.x-1.x
I have created a patch where fieldgroups are added to the $all_children array and the format_type is set to "hidden" for those which are not in the current step.
It could be related with the issue Compatibility with field_group >= 8.3.3 🐛 Compatibility with field_group >= 8.3.3 RTBC . The patch #2 → worked for me.