Ownership is being conferred by purchasing immich, that’s what the product key codes they’ve started using indicate.
That is the fundamemental change in the way they are offering Immich: if you pay, you are provided with proof of ownership (product key). If you don’t, you are using it as a part of an indefinent trial period.
I’ve never had NewPipe present me with a sign in prompt or any bot challenges, that’s a very strange scenario to be facing.