I don't see how phenomenological bridges solve the epistemological problem, instead of just pushing the problem one step further away. Where in the bridge hypothesis is it encoded that one end of the bridge has a "self", in a way that leads to different behavior?

Let me give an example of AIXI, which creates something that is almost a phenomenological bridge, but remains Cartesian. Imagine that an AIXI finds a magnifying glass. It holds the magnifying glass near its camera, and at the correct focal distance, everything in {world − magnifying glass} looks the same, except upside down. Through experimentation and observation, it realizes that gravity hasn't flipped, it's still on the ground, the lights are still 15 feet above it, etc. It will conclude that the magnifying glass filters visual input on the rest of the world flipping the Y axis. Thus AIXI has a hypothesis about the relation of the magnifying glass with the world.

Phenomenal bridge hypotheses are saying there is something like this magnifying glass, except embedded in...where? What's the difference between reading glasses and retinas? I can have 1 "visual filter hypothesis", 2 visual filter hypotheses, n visual filter hypotheses. What's the distinction between internal filters and world filters? Do I have x internal filters and {n − x} external filters? What would that mean?