For anyone experiencing this issue after updating to KB5065789. TeraCopy can be used as a workaround to compare copied files again. It used its own dialog, has more options and can be set as the default file copy handler. Get it here: TeraCopy
There is an open Feedback Ticket for this, many are having the same issue. Upvote the problem and maybe they will fix it some day… https://aka.ms/AAy6aif