Next door dog yapping at 6am

[Macaroni46]

My next door neighbours have two terrier type dogs that yap a lot. I've got used to this during the day - they let the dogs wander around in the garden for hours while they WFH and the dogs yap intermittently.
My gripe is the early mornings. For example, today I was woken by the sound of them yapping at 6am. I presume they'd been let out to do a wee. But the barking woke me up and I've been awake ever since.
Would it be worth saying something to them or is this just something I have to accept living next door? I've never owned a dog so I don't know if they can stop the yapping. I presume the dogs are being let out at 6am because they need to go to the toilet.
So my question is: should I say something or would that be unreasonable / there's nothing that can be done?

I imagine there is something they could do to stop the yapping at that time in the morning. But it depends on what kind of people they are whether they agree to try. I’d be mortified if this was me as a dog owner and I’d be doing everything I could to avoid it. If they just bark as soon as they are let outside this would be harder to deal with but if they are barking because they want to come back in, this would be much easier to address.