Is there any free MDM Solution ?

I work in a hotel and we are deploying a new app which requires at least 10-15 phones I want to manage these phones features like locking the parameters; blacklisting certain sites etc.. (administration phones are already enrolled with intune and managed by an MSP) but these phones will be handed to cashiers and servers and I want to be the one managing them.. that's why I'm not going to Be enrolling them with intune