There's your problem, you rented a terminal managed by the fruit factory so they get to decide who the thing serves. Either "jailbreak" the thing or get a Google-free Android device with an AOSP-derived distribution on it. I have the latter and I don't see any ads.

Windows... same thing. Avoid it if you can and yes, you can unless your employer forces it upon you. In that case see if you can use the LTSP version since that isn't as laden with spy- and adware as the regular versions.

Browsers? Firefox or one of its derivatives help to get rid of ads and other nuisances. I don't see any ads on either mobile or X-top, they don't seem to make it through the combination of network, host and application-level filtering. Those filters just work without needing maintenance, you just need to put them in place.

As to that elevator blasting ads you're more or less on the same situation. The only way to avoid that would be to make sure you manage your own environment. Doing so is much more involving than changing from a fruit phone to something under your own control. I live on a farm in the Swedish countryside where ads just don't seem to thrive, I understand this isn't for everyone but if you're serious in wanting to escape there'll be something similar available in whatever country you call your own.