It's easy to select an object and all its duplicates in a scene. Just SHIFT+L and Select Linked > Object Data. But Blender will only select duplicates of an ACTIVE object, not all selected objects if there are many in the selection. Let's say I selected 10 objects - each having their own bunch of duplicates in the scene, but not being duplicates to each other. I can't just select in one go all duplicates of these 10 objects.
Ofc. I can use some workarounds, e.g. selection sets. There is a paid addon for that. Or use a collection to put there all stuff that I will need to quickly select in the future. But I would like not to mess with my model hierarchy. I would like a feature like "select all duplicates (linked data objects) of all selected objects". Is there something like this in Blender?