It seems there are a lot of variations based on a central theme: What are the requirements to use magic items and who can use them?
Within that scope there are variations of magic items (We can ignore items with prerequisites as they are generally more self-evident of who can use them):
- The Ring of Spell Storing as a specific case; there may be more
- Normal beasts
- Awakened beasts
- Spectral forces (Unseen Servant, Tiny Servant, etc)
Between all that there are a dozen or more combinations; but with minor redundancy. Each must be answered in some fashion, but they are interdependent of each other. People are asking the question(s) in one-to-one relations, many-to-one relations, and one-to-many relations.
- Can a familiar (one) use a Ring of Spell Storing (one)?
- Can Awakened beasts (one) use magic items (many)?
- What normal creatures/beasts (many) can use attuned magic items (one)?
With all that said, could we really have a single question that requires the answerer to explain the whole matrix of possibilities; many-to-many? They would have to justify every combination, every permutation. While possible, it's not likely. Unless they were allowed to build their logic based on other sub/duplicate questions.
The problem comes from this being a strictly Q&A medium. Good answers need to have valid references and solid reasoning; and when the source material doesn't present the fact plainly, we rely on other questions/answers to build up a logical conclusion. So there needs to be minor questions that appear as duplicates but are actually handling specific cross-categories to be building blocks to create a foundation for the ultimate matrix.
So to that end, I would target the one-to-one style questions and mark them as duplicates of the many-to-one/one-to-many questions. We can also safely mark duplicate those that are completely redundant; A familiar is a familiar, even if they are Pact of the Chain. An owl, a pig, a snake, and a fish have similar stats when considering attunement and only really differ in physiology which is a completely different subject.
But I think there needs to be a certain amount of overlap, or perceived overlap, as each of the variations I mentioned carry unique constraints.
Specific dupe/reopen suggestions
I've evaluated each of the RPG.SE questions you linked regarding which ones should stay open and which ones should be closed as duplicates of others (I reordered a few entries from your list to put them next to the questions they should be closed as a duplicate of):
The 2 pairs of questions at the bottom of your post have correctly been closed as duplicates.