I've never had one, but I don't see why it should be any different from a separate washer and dryer. Smell from a dryer is often the lint filter and many combined washer dryers do not have a long filter. As long as you keep the drum and pump filter clean, as you would with a washer, then I am not sure where the smell would com from. I'd be curious to see if anyone does have issues with them.

*do not have a lint filter

Our FL washer is 9 1/2 years old and no smell.

This post is about a front load washer -- not sure if you meant a FL washer, or a combination washer/dryer unit (all in one machine):

Yes! I've used them for almost 20 years, and I'll never go back to a top-loader again.

The smell some people face is from water that pools in the gasket around the door (especially at lower spin speeds) because gravity can't pull it away -- so leave the door open a few inches for it to evaporate. If I have a lot of water there, I will sometimes put a clean rag in that spot to soak up the excess. They do as a good job, but with less water and energy use - and because there's less water in your clothes at the end of the cycle, they allow your clothes to dry faster (so less energy used there too). The cycles do take longer than a standard front loader, but I'm OK with that as a trade off for using less energy and water. I put a load in at night, set the delay start, and then toss the just-finished load in the dryer in the morning.

I read, albeit a couple of years ago, that combo washer dryers use more water, not less, because the condenser uses water to cool the air.

@Toronto Veterinarian, I realize you are talking about front loader vs. top loader, whereas I read 'washer/dryer' as meaning the combo machines.
I would never want to go back to a top loader. I associate them with my 70s childhood and having to use laundrettes at college. I couldn't justify using that much water and electricity at home.

"whereas I read 'washer/dryer' as meaning the combo machines."

Yes, when I read your posts I realized that that might be the case......I'm not sure what the OP meant.

Washer/dryer combo typically refers to a pair of machines ... a washer and a dryer.

I expect that the majority of consumers nowadays are not aware of true combos ... one machine that performs both functions. Those were offered by all major brands on the U.S. market from the 1950s to 1970s (Kenmore held out the longest). They've made a bit of a comeback but are a niche market.

If that really is the question I agree with @Susie. In 50+ years of doing laundry with a variety of different water supplies and machines, I've never come across an issue with smell.

Yes thank you everyone. sorry I wasn’t clear but I did mean thoughts on front load washers & dryers (not as one unit). I read about the smell being awful and unavoidable but I have hope now. 🙌🏻 Thanks for the feedback!