Is it possible to allow sideloading and keep users safe?

"sideloading" connotates something that is negative.

On systems before apple's locked-down iphone, it was just called "installing".

The PC revolution started with people just inserting their software into the comptuer and running it. You didn't have to ask the computer manufacturer or the OS vendor permission to do it.

And note that apple doesn't allow you to protect yourself. You cannot install a firewall and block arbitrary software on your phone. For example, you can not block apple telemetry.

1. I buy computer hardware, like an iPhone

2. I try to install my own software.

3. I'm prevented in installing my software on my device without "permission" from manufacturer.

4. Therefore, I do not own said hardware; manufacturer still does.

5. Therefore this is a indefinite rental instead of a sale.

6. I was defrauded with a fake sale, and Apple is defrauding IRS by not being properly taxed over millions of rental units (phones, tablets)

You can install your own OS on iPhone hardware, what you’re demanding is that Apple allow you to run your own software on their OS. It’s like saying that you don’t own your microwave or lawnmower unless they provide you with an API to build apps on it. Are you just renting your Xbox because you can’t run PlayStation games on it?

This is a ridiculous argument.

I have a purely mechanical lawn mower. I can replace any part of the engine, frame, switches, I can add a second engine if I wanted to.

An Iphone doesn't let you do any of this. "Their OS", no dude, I bought it, it's in my hand.

You conveniently ignored the Xbox example, why don’t you address that?