Any cheaper or self-hosted alternatives to Hexnode for Apple devices?

Check out the built-in device management in Apple Business Manager first. It's free where available and might cover such a short requirements list without another service to host.

The interface is fairly basic, and some settings may need custom configuration profiles. Check remote wipe, your specific restrictions, and wallpaper support for each device type before switching.

For self-hosting, take a look at NanoMDM or Fleet MDM. NanoMDM is worth investigating if you're comfortable building and operating more of the management setup yourself. Check which features each supports before committing, especially wallpaper and the restrictions you need.

I wouldn't jump straight to coding an MDM just because the feature list is short. You'll still own the server, security, maintenance, and the reliability of remote wipe when a device goes missing.

If the goal is mostly to cut the bill, a cheaper hosted service may be less work than running your own. Mosyle and SimpleMDM are both worth pricing for an Apple-only fleet. Compare their current plans against those three requirements, since pricing and included features can change.

Already paying for Microsoft 365? Check whether your licenses include Intune. If they do, it could be an option without adding another MDM bill. Configuration for iPhones and iPads is generally straightforward, but check the Mac settings separately if those are part of the fleet.