Not all lactose free milk is equal. Look for ultra-filtered lactose free milk. The extra sweetness is caused by adding an enzyme that breaks down lactose into smaller, simpler sugars, e.g. glucose. Your body is better at tasting these sugars, and so you notice the sweetness more.

Ultra-filtered milk removes the brunt of the lactose before they add the latase enzyme, and thus there will be less simple sugar for your body to notice, resulting in a less-sweet milk.

Oat milk or water won’t add the body or depth you’re looking for. Depending on the particular beans, roast, and brewing method, milk might enhance the flavor profile. Similar to sugar and salt enhancing cacao. Yes, you lose nuanced notes, but no, that’s not a bad thing if the overall profile is improved.

You can also try blending different milks. Maybe you like 90-10 oat/whole milk or 70:30 ultra filtered/macadamia.

Perhaps go to a local shop during a slow period and ask if you can get a cup of coffee black and a flight of alternative milks. Whatever you do, have fun doing it!

A friend recommended Oat milk to me - I’m exactly the same as you re disliking the sweetness of lactose free - she reckons it’s ‘inoffensive’.

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 😅

My vegan coworker uses sweet vanilla soy milk most days, but plain soy milk on others.

If it’s too sweet, consider doing 50/50 with water.

I had the same issue a half a decade ago and my solution was, like most of the answers I imagine you’ll get here, to just get better coffee and drink it black. If you visit your local third wave cafes they should have a regular rotation of drip specialty coffee that you could try and usually they sell it too. I order from Th3rd Wave which sends me a box of different specialty coffees every month which really helps me discover what’s out there, maybe you have something similar in your area?

Brew better coffee so you don’t need milk? Try some light roast beans.

I was able to cut out milk entirely first from my filter coffee and then from my moka pot coffee just by using better freshly roasted and light roasted beans.

Oat milk and coffee taste like they’re meant to be together.

Just make sure it’s a good Oat Milk. The Chobani extra creamy is my favorite.

Another idea is to drop some coconut oil into the coffee. It’s different but it’s something and you don’t taste the coconut if you get refined oil.

Whiskey

I usually do oat milk, it’s not bad

A friend recently made me black coffee with a little honey and it was excellent. There was only enough honey to take the bitter edge off the coffee without getting too sweet. Although my friend did use some high quality beans I wouldnt normally use so I’m not sure it will work on the cheap stuff most commercial places use.

I know you’ve already gotten a bunch of answers including the going black option that I’m chiming in with… But I went through a similar process a few years back now. It took experimenting with lots of different brands until I found one that I could happily drink black. Not sure where you’re located, but I found a local roaster that I’ve been super pleased with. It’s called Goshen. It’s more expensive coffee but it’s also ruined a lot of other coffee for me now

Almond milk. Non-sweet is an option.

Soy milk! You can find no sugars added options

Another vote from me for out and almond milk. If you do any kind of milk steaming or latte art then oat is great for that…and I just like the flavour of almond milk. It’s really nice with breakfast cereals too as it adds a nice nutty flavour to everything.

There is nothing wrong with Soy milk, but with coffee you have to be careful you don’t curdle it due to the high temperature.

Oat milk is the best alternative I’ve found. Most places offer it so I switched to oat milk lattes and haven’t gone back.

If brewing at home, there are barista versions made specifically for coffee, but the original works too.