"side loading" in the EU still requires you to have your app reviewed and notarized by apple, which means you can't call private APIs.

You also still need to pay $100/year developer fee for your app to continue to be side-loadable (otherwise they revoke the notarization), and need to pay the €0.50 "core technology fee" per side-load to apple after a free allowance of side-loads.

I doubt it's going to help pebble since they'll have to pay more for users to side-load the app than to install it from the app store.

https://doesioshavesideloadingyet.com/