I think the minute you have hybrid, the water-cooler chats return. You can call them “secret” or you can call them “casual and opportunistic”, but they’re going to happen and they’re sometimes going to spawn a good idea.

Then you might force people to memorialize that idea in some form, but you can’t/shouldn’t/can’t stop people from chatting in the break areas and, especially at the start of hybrid, it’s going to be very fertile ground that your company should encourage and foster (and maybe channel) rather than taking steps to discourage. “Sorry Pat, you know the rules; we’re not allowed to speak except on slack.”