at least all the modern ones i've seen, you cannot open them all the way using only manual and without power, because it's not good for the motors. or maybe that's one of those common myths.

The manuals I've looked at say something like "don't open it without power, it may damage things. If you have to open it without power, be careful."

At least the Kia mentions non-power doors, so even if not available in the USA they're made somewhere for some market. If you really wanted to, you could probably import the parts and swap.

Ah, I see! I have a Toyota Vellfire and you can just turn the power doors off, when you do that they behave exactly like non-power doors. When I was over in Austin recently I got a ride in a Sienna taxi and the back doors were manual in that, so presumably that model lets you switch them off too.