I would have recommended oat, but if you say lactose free milk is already too sweet I think you’re likely to find the same with oat. Macadamia is probably the “creamiest” non-sweet alternative I’ve tried, give it a shot.
That being said, stay open to the idea of cutting back on additives altogether. I went through all sorts of things just to discover that what I liked wasn’t a particular creamer or sweetener or coffee brand - it was just lighter roasted coffee 😅