Towing issue

With an older AWD Toad you have an issue when towing because the differentials are being driven by the tires, now those are in an oil bath for the most part so they are not a big issue normally. The drive shafts on them however, spin and turn the transfer case parts. These are where you have an issue, when the engine is running and powering the vehicle the input shaft on the T-Case is spinning and that drives an oil pump in the case which lubes all the parts. When the case is being spun by the output side that pump isn't operating because the case is normally in neutral. So what you do is start the engine, run the transmission through the gears and that turns the pump to lube everything and keep the bearings from burning up.

However, on the new Blazer they are a lot different. On most "modern" AWD vehicles they are not rear wheel drives with a big transfer case like the older ones, instead they start out as a front wheel drive vehicle. Then they use what amounts to a power takeoff assembly installed on the transmission that turns a right-angle gearbox that spins an output shaft that powers the rear driveshaft. The power transfer unit isn't a big deal as most either share lube with the transmission or have their own oil bath. The issue is usually with the rear differentials or the transmission itself. Both have pumps in them that lube the various parts, with the transmissions you have some parts spinning that are not being lubricated.
Plus, they are under a heavier load because they are spinning freely without being under clamping pressure. So, a set of clutches in the transmission would normally be squeezed between the drum and piston, that holds them to transfer power but it also acts as a structural brace to hold the pieces together. Without that force you can actually cause the parts to spin apart and fail. So, they limit the speed you tow to keep the centrifugal forces down below the likely damage speeds. This applies to the rear differential as well as it has the clutches in it that function as the transfer case.
So, they tell you to run slower and start the engine now and then to lubricate the various parts. Most of the folks I know who run wheels down with AWD will do is to stop every 4 hours or so, they check the tow systems, verify the lights and tires are okay, wipe off the cameras, stretch their legs and such things. They will also start the car up, run the transmission through the gears while holding the brakes and then put it back into neutral and shut it off. Then continue on their way.
Your Blazer uses a GKN 761 PTU that has different driving modes. In Touring mode, you have front wheel drive only. All the other modes engage the AWD section in one way or another. The attached images are the exterior and the internal gearing, The gears are not the issue themselves, inside they have the clutches (item4) that spin freely while towing.
GM says they can be towed 4 down so I would trust them somewhat, however I would also have the front PTU and rear differential serviced more than the book calls for, just to keep fresh oil in them and help them live longer. One thing though, being a 2021 I would probably pay the dealer to do those services and keep good records of all service done while under warranty. Once it's out of warranty then you can DIY it but GM has been fussy lately about warranty claims with any unusual vehicle use, even if the book and dealer says things are okay to do (so have many other companies).
One other thing, watch the tire wear, Most Toads tend to wear them faster due to the towing aspect than if you were driving them. Enjoy your travels.