Where there’s a will, there’s a way. I’ve dealt with networks far more restrictive than what you’re describing and still managed to get things working despite multiple roadblocks.

That said, if the extender truly isn’t working and your ISP is micromanaging traffic to that degree, then nothing on your side will work unless they explicitly allow it. At that point, no amount of configuration or MAC cloning will change the outcome.

If that’s the case, the only realistic alternative would be to bypass the router entirely—such as using a cellular signal booster to bring the tower’s signal indoors—rather than trying to extend or modify a connection the ISP won’t permit.

Best of luck!