Neither approval, nor disapproval just straight up quagmire.
There’s no silver bullet to getting things done successfully in any large organisation of humans.
That's ok. Setup a meeting with said stakeholder, clarify your position, ask for input, and in the end ask straight up if they have any objection. Save the meeting minute and send it to everyone who attended the meeting.
They need to put up or shut up. Playing games does not work.
There is no silver bullet. You have to treat each one in the way that works for them. Those who do it well, it's a talent.
Or have the compromising photos of the boss and copies of the bank statements so he's scared and backs you publically always and then just roll anyone who isn't effusively enthusiastic. That works too. Wouldn't recommend it.