I know this is semantics, but people don’t believe in their religions, they practice their religions’ precepts, customs, dogma, etc, that revolve around a belief in a deity. That deity may be mono or polytheistic or tripartate.
I am on a local commission made up of adherents of various faiths. Every time a ‘religious leader’ attempts to start the meeting with a ‘universal’ prayer and a statement that their is only one ‘god’ I challenge it and say there is no universal prayer and while each of the 3 major religions stemming from Avraham may be ascribed by you to have the same ‘god’ there are members of this commission who are Buddhist, Hindi, Sikh and Native American who worship multiple gods. Lets leave all religion out of the government commission.