Just to add...

Free stopover hotels etc where available are usually only offered by most airlines to revenue passengers who have also selected the shortest possible connection (but which is still longer than some minimum threshold, often 8 or 10 or 12 hours), or to those suffering significant delays. A Sindbad redemption would not get one in my experience. A redemption through another programme would likely be entering lottery winner territory in terms of expecting WY to cough up.

Please do not get excited about the landside arrivals lounge. It's a nice room but not really set up as a destination in itself, and in my experience not catered anything like the airside lounges.

The airside lounges are good (including the non-WY ones), but if you are staying in Muscat for long enough to be worth leaving the airport you will find better food ex-airport, as you would anywhere.

I really like the now new(ish) MCT airport. But I would always head out if I were there (or anywhere else) on a very long connection. Bear in mind though that taxis in Oman aren't as cheap as they might be in neighbouring states. So if you are leaving the airport, I would recommend heading to a hotel that is walkable to wherever you might want to see whilst you are there.