Is it possible to allow sideloading and keep users safe?

Yes. It is a basic human right.

> This is a question where freedom, practicality, and reality all collide into a mess.

No; it isn't. The answer is clear and not messy. If you are not allowed to run programs of your choice, then it is not your hardware. Practicality and "reality" (whatever that means) are irrelevant issues here.

Maybe you prefer to use hardware that is not yours, but that is a different question.

The social structure of the smartphone app ecosystem is remarkably similar to the cable provider -> network -> show situation from before too.

They’re clearly just computers, they’re “hardware you own”, but you’ve never been able to run whatever software you want on them. But it’s been like this since the 1970’s and there’s never been an uproar over it.

For me the difference is that you know what you’re getting into when you buy a console, and it’s clear up front that it’s not for “general” computing. I’m inclined to put smart phones into this category as well, but I can see how reasonable people may disagree here.