As a former Cub owner, I did some research on ADSB rule airspace a few years ago. Basically, 91.225e says that if your aircraft has never been certificated with an electrical system, you can fly in the mode C veil and you can fly above 10,000' msl without ADSB.
That's about it though; similar to other non-equipped aircraft, you still can't fly in class A, and you can't fly in or above class B or C.
You can can fly in class D if you have a standalone radio that is sufficient to make the initial 5-7 mile call to the tower. I tried it once in the Cub with a handheld radio, but couldn't get a response.