This is the unfortunate reality of current intellectual property. Anytime you don’t have a copy of something directly in your possession, either as a physical object like a BluRay, or digital file(s) on digital storage only you control, you don’t really own it. You’re just borrowing it, or more strictly speaking, you’re purchasing the right to access it until the agreement between the creator company (i.e., WarnerDiscovery) and the hosting company (i.e., Sony) expires.
When issues like this come up, there are right ways and wrong ways to handle it. This is an example of a wrong way. Google’s handling of the Stadia shutdown was an example of the right way. Any game you purchased on Stadia was refunded to the original payment method, not store credit, at the price you paid giving you the ability to reacquire the game on another platform and/or in another medium. They even refunded in-game purchases of things like premium currency (e.g. silver in Destiny 2, or crowns in Elder Scrolls Online) which was a great bonus because you got that whether you had spent the in-game currency or not so it was essentially free.
Personally, I’d like protection like what Google offered to be legally mandated for the purchase of streaming content. Sony has little choice in the matter if WarnerDiscovery won’t renew the streaming license. Legally, they must revoke access to the content, but currently they can choose to not compensate users who lose access to the content through these legal machinations and that’s what I have a problem with.
That’s an iOS/iPadOS thing. Mac browsers can use any rendering engine they want.