McDonald's fryers are generally just standard commercial fryers with preset temperatures and timers. The only custom part is the (separate and standalone) machine that measures out standardized portions of fries into baskets, and while I'm sure they'd call it a trade secret it's really just a big plastic hopper and some sort of weight sensor arrangement.

Did McDonalds ever adopt the ones with built-in cleaning systems?

They really are that expensive, and not just the robotic ones.

Perhaps with the entire hood/exhaust and fire suppression system. But not a simple two basket fryer. When I bought mine (new) in 1995, they were roughly $3K. And this had a built-in filtering system.

Actually, to spend $50K on a fryer system is pretty hard:

https://www.webstaurantstore.com/63853/deep-fryer-with-oil-f...