Is it possible to allow sideloading and keep users safe?

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.

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)

Want to renovate and change your home that you own? You need permitting and not all changes are allowed. But you own the home and land so why do you need permitting?

Say you want to modify your car that you own, again depending on the modification that's technically not allowed either (an aerodynamic wing in a place like Japan, for instance, can't be certain dimensions; but if you own the car you should be able to do what you want with it).

Maybe none of these types of things should be beholden to someone holding the reins of the thing you own but it's not like Apple not allowing sideloading is some wholly unique problem.