I can't disable the lock screen!

Clearing the credentials or permissions won't erase your phone. A factory reset will definitely erase EVERYTHING from your phone, it'll be back to the state it was when you first bought it.

You could try factory resetting your mobile device.

On my alcatel idol4 there is no "device reset", this lock screen is really upsetting. Any progress without reset to factory ?

Alcatel has a built in security setup that disables the swipe lock screen option after removed if a account has been linked to the phone. Follow these steps to reset lock screen back to swipe without factory reset. First, Back up all account information to the linked google account. Second, Remove account from phone. Third, got to Settings>Security and remove all settings that's been checked. Last, Clear credentials and your done. Now go to Settings>lock screen and the option will be opened.

When you go into settings go to security and then scroll down to trust agents, take off Google smart lock and then you can take off your lock screen, I have the same phone and the same problem but I just figured it out and did it and it worked. Hope this helps