In theory you can do the same with Signal, as they source dump their server code every now and then.
If you reject that on the basis of "we can't know if it's what they're running" or "it's a partial dump", then I don't see how Matrix is any different. Not only we can't know if Matrix servers have modified software, but we also have to trust/verify several servers instead of a single one.
If you reject that on the basis of "we can't know if it's what they're running" or "it's a partial dump", then I don't see how Matrix is any different. Not only we can't know if Matrix servers have modified software, but we also have to trust/verify several servers instead of a single one.