Have a loved one that lives in MI. Looking for self defense options and came across this keychain.
https://noveske.com/products/noveske-equalizer-keychain/
Is it legal to own in MI?

Any other non firearm/non mace options you'd recommend?

As with all things, you will be given the opportunity to prove it is legal.  It will be in court and cost thousands of dollars.

MI law clearly states “metallic knuckles”. If this is plastic or something like that, sure. It’s legal.
But every cop is going to cite you or arrest you for it.

Just carry a gun.

If one does decide to carry this, understand it has little effectiveness against a truly determined attacker.

Unfortunately, the person in question does not want a gun at this time. I've given them fox labs 5.3 pepper spray for something atleast.
The language of "metallic" is indeed in the statute from what I've read, and found that contrary to Google's pre qued question /answer on my search which states the "Stabby Cat" plastic keychain is illegal -- quite contradictory. I do see your point about it being a case to prove, wasnt sure if one has been elucidated in detail in MI as search results are slim. In MN, we can get these Equalizer Keychains right at Scheels (sporting goods store) nilly willy like buying beef jerky!

I would also make sure the fox labs is below the legal amount of spray for a person to carry.

Indeed, 1.2 oz max so that was limited to a key chain size unit of 1/2 oz, next size up is 2oz

Dumb as fuck