I don’t want my litter box to become useless because an app stops working

I’m comparing PetPivot and PETKIT from a slightly boring angle: what still works if I stop using the app entirely? I’m fine with an app being optional, but I don’t want basic cleaning to depend on a phone, an account, a server, or whatever software still exists years from now. For something mechanical that’s supposed to live in the house every day, physical controls, replaceable wear parts, access to basic troubleshooting info, and the ability to keep running offline matter more to me than getting another notification. I also want to know whether common parts can be replaced individually instead of turning one failed component into a whole-unit replacement. I’m not calling either brand “buy it for life” because there simply isn’t decades of history here. For owners who avoid apps, which basic functions still work normally offline, and what part availability would you check before buying?