Holding silver and trading it on margin are two questions
A ruling that permits owning silver settles the question of ownership. It says nothing about a leveraged derivative on the price of silver, because a derivative introduces features that classical fiqh examines on their own terms: borrowed exposure, a periodic payment between counterparties, and a contract that never delivers the underlying to anyone.
Those features are argued separately in the literature. Leverage raises the question of a loan and of what is paid for it. The funding payment exchanged between longs and shorts every 1h raises its own question about what that payment is compensation for. The absence of delivery raises the question of selling what one does not possess. Each of those has its own record, and none of them is answered by a ruling about silver itself.
What Canborsa actually lists
Every market on Canborsa is a perpetual — a leveraged contract on a price, with no ownership of the underlying at any point. A reader who is here for the spot question is reading about a different instrument than the one this venue offers, and we would rather say that plainly than let the page imply otherwise.
Canborsa makes no claim of Sharia compliance for any market it lists, and offers no screened or certified account. Nothing on this page is a religious ruling.