Grammatically, the location of the apostrophe makes parent singular. However, it seems weird if I think of it that way, likely because pronunciation as a whole is the same regardless of parent being singular or plural. Computers is plural regardless. This really doesn't effect me ib any way, but somehow seeing someone else want to know makes me want to know.

"What did you replace Windows with?"

Haiku probably ... s/

The only real alternative option with most hardware is linux. And when the use case is browsing the internet and you are there to help them unstuck a broken update, things should be fine.