Second list you could manage with a dispatcher. Trouble with dispatchers is you have to know the type of object you are binding to, but apart from that, one call will notify all bound actors.
First list you will need to manage. If you don’t want to get a ref to your GC, you can use something like the game instance. Yes you have to use ‘get game instance’, but then it’s a generic type, and you can call your interface on it, without causing any tight coupling. So some way of talking to your GC from the game instance, or just putting the code in the game instance would work there.