I don't appear to have that "Don't Host Online" option, neither in a New Meeting nor in the Customize The Ribbon.
Regardless, you shouldn't need to customize the ribbon just to be able to remove an embedded meeting link. Please, MS, just enable removing any linked/embedded meeting as a part of the interface.
Recommendation #1: If there's an embedded Teams meeting, the button should change from "Join Teams Meeting" to "Remove Teams Meeting" when in Edit mode.
Also, this can make using Microsoft Teams Rooms devices quite frustrating to use (or impossible if the Org policy setting is to automatically add a Teams Meeting to all new meetings) to join "external" meetings. If it's impossible to replace an embedded Teams meeting, then there's no way to get the MTR to offer to join a Zoom or WebEx meeting.
Recommendation #2: If there are multiple kinds of Join links in a meeting, the MTR should offer to join each. There's plenty of room for more "Join" buttons on the interface, and/or a dialog could pop-up asking which meeting to join (and maybe showing the # of participants in each).