I’ve previously used: https://www.macincloud.com/
And then just legitimately register any freaking iOS device of any rando on your developer account (don’t even need your account on the device at all), and that’s all Apple cares about. You don’t even need to actually test the app on any iOS device first, just have a device listed on the account. There’s so much that’s so patently ridiculous of policy/procedure of publishing anything to any Apple platform.
Nonetheless, this is +7 year old advice, as I don’t know how much it’s changed since then (other than not requiring $100/year anymore for the ‘privilege’ of developing for iOS).