My Cayenne’s making a worrying noise from the rear diff

So I’ve got a 2018 Cayenne that’s been absolutely flawless up until a few weeks ago, and now I’m starting to hear this low humming noise that seems to come from the back end, especially when I’m coasting at around 60-80 km/h. It’s not super loud yet but it’s definitely noticeable and I know from past experience that these things rarely just go away on their own. I’ve done the obvious stuff like checking tire pressure and making sure nothing’s stuck underneath, but the noise persists and I’m starting to get a bit anxious about it. A mate of mine who’s a bit of a Porsche enthusiast mentioned it could be the diff fluid or maybe even a bearing starting to fail, which sounds expensive if I’m being honest. I really don’t want to gamble with a general workshop because these cars are so particular about the right fluids and procedures, and I’ve heard horror stories about places using the wrong spec oil and causing bigger problems down the line. I found some information about Trusted Porsche repair specialists in Musaffah Shabiya and it looked encouraging from what I could see, but I’d love to hear from anyone here who’s actually used them or knows of a place that properly understands these vehicles. I’m willing to travel a bit if it means getting the job done right, I just want peace of mind more than anything.