Illegally installed MDM and invalid Root Certificate

There is no such thing as an unauthorized MDM. To install MDM, you either

1. Must purchase the device from Apple or an authorized reseller and have it added to Apple Business/School Manager and have an MDM connected for automated device enrollment
2. Someone must have physical access to your device and must have your passcode/password.
3. Someone must have physical access to your device, your iCloud password (assuming you've set that up), and be in a trusted location (or wait for an hour, again, assuming you set iCloud up), then they have to wipe your device and add it to Apple Business/School Manager manually.

Option 1 cannot be removed by you because you don't own the device.

Option 2 can be removed in Settings > General > VPN & Device Management.

Option 3 can also be removed in Settings > General > VPN & Device Management if it has been less than 30 days since the device was enrolled. You would likely notice if this one was the case as again, at a minimum, it requires the device to be wiped.

These are the only options.

What Mdm is installed at

Settings > General > VPN & Device Management

Who installed the MDM?

Settings > General > VPN & Device Management. Can you provide a screenshot?

Same for the Root Certificate

Sorry you have not provided any information:

• What is the invalid Root Certificate?
• What MDM is showing in Settings?
• How did this MDM get installed?