Apparently, content blockers work on 32-bit CPUs, but Apple is restricting them on the store to 64-bit only. So you can go the BlockParty + EasyList route: https://github.com/krishkumar/BlockParty

It works very well.

Note: Apps containing content blocking extensions for Safari on iOS are available only on 64-bit devices, due to performance limitations of 32-bit devices.

https://developer.apple.com/library/prerelease/ios/releaseno...

I imagine there's no real reason that content blocking shouldn't work on 32-bit devices, but that Apple are trying to hit certain minimum performance numbers (for marketing/brand purposes)... and I'm sure they won't be upset if this should happen to encourage a few users of older devices to upgrade (i.e. forced obsolescence).

I think there are various examples of Apple doing this kind of thing (saying a certain generation of hardware is supported by software X, but then you find various things are disabled for you). Not exactly the same, but pre-2011 Macs cannot mirror their display via AirPlay (Apple saying the video hardware isn't up to the task) -- at least not until you install the third-party app AirParrot, then it works fine.

[1] https://developer.apple.com/library/prerelease/ios/releaseno...

For those doubting ad-blocking works on 32-bit ARM, have a look at the multitude of Android devices. Nearly all of them use a 32 bit CPU. Many of them run some form of ad-blocking software, ranging from proxy-based systems (a la privoxy) to browser plugins to host-based blocking. Often a combination of these are used, all on those 32 bit CPU's.