Consider this though.

In the case of Britain, they got the artifacts because they established a protectorate over Egypt and thus were able to excavate and do civil engineering.

However, the fact that the artifacts were there to be discovered in the first place was because the Arab and later Ottoman overlords left them there.

So who should rightfully claim them? One of the historical suzerains of Egypt? Or the current nation of Egypt who inhabit the ancient Egyptian territory?

I can’t think of the ‘right’ (ie just) answer to that question… only practical ones.