Generally, as far as I understand side loaded apps work as long as you don't reboot your phone. Which is kind of a major issue. Someone correct me if I'm wrong, but I'm pretty sure the way apples current side loading works just isn't very applicable with day-to-day use.

Edit: you may be able to bypass this restriction, but as far as I know side loading apps onto Apple phones is extremely difficult. Even jailbreaking an iPhone is extremely limited unless you have a really comprehensive knowledge and then even at that point it is still extremely difficult and relies on people who are very good at what they do. But due to apples restrictions are still not as good as just something you could do out of the box with an Android. In full disclosure, it's been a very long time since I've ever properly used an Apple product. The last time i jail broke something from Apple was probably my iTouch B way back in like 2014 at the latest maybe? I just haven't been within that ecosystem in a long time and all my knowledge is just really acquired from kind of observing what is around. And cursorly looking into it. For me, I have no reason to ever want to go back to an iPhone. Even if I could side load apps, the restriction of where I can place icons on my home screen frustrates me to no end. Especially as phones have evolved and gotten larger its just like it's such a old school bygone concept. I don't even understand why they're so insistent on keeping it.

As long as the app doesn't need advanced features like VPN configurations, any app from any region would be fine.