Can I enroll my personal iPhone in MDM myself? And if I can have MDM with just my personal phone, do I need to buy some kind of subscription for it from Apple? Or pay some third-party?

I thought MDM was only for enterprise businesses and schools and universities, but I may very well be mistaken about that.

MDM profiles are just XML files. They can be created with any text editor and distributed to the phone by email or web server. Apple provides the free "Apple Configurator" app in the MacOS app store. There are also websites and/or OSS tools to generate profiles, e.g. https://github.com/ProfileCreator/ProfileCreator.

Apple supplies a free application for managing MDM.

https://support.apple.com/guide/apple-configurator-mac/welco...

^^^ Highly recommend this. If you are technical enough, a family managed Apple Configuration is more than enough to protect for most situations and from most threat actors.

If you're threat actor has the resource to break that, get a CC or a good lawyer on retainer I guess.

This saved me one time when I was gifted an Apple TV without a remote.

No way to add a WiFi profile, thus no way to use an iPhone as a remote. No ethernet available either.

Configured a WiFi profile, uploaded to the Apple TV and could finalize the setup.

It’s quite a powerful too for initial setup.

Looks like an easy task, even your granny can do it.

It does require a few clicks and passcode entry, https://support.apple.com/en-us/102400

Why do you need a Mac and an additional software for this? This is clearly made for corporate users and not for ordinary people.

Mac is not needed, https://news.ycombinator.com/item?id=41351559

After an MDM profile is created by someone technical, it can be emailed to the non-technical user and installed with a few clicks and passcode confirmation.