I have found gearbox oil ( about 75w) to be satisfactory.

Now I will apologise beforehand for a little rant.

Years ago all old Brit bikes and others had breathers that tended to eject a little oil mist especially on start up. This was usually directed at the rear chain. My old Triumph had a timed breather (from teh inlet camshaft) that was directed directly on to the rear chain as it ran over the gearbox sprocket.
Naturally from time to time a little oil would flink off an hit the rear of the crankcase and when parked from time to time a drip or two would run down the crankcase and fall to the floor. Those unknowledgeable would declare it an oil leak. But it was designed to work that way. The great gods in their ivory towers decided this was a bad thing and declared oil was a pollutant. so the bikes were re-engineered so that any crankcase pressure is now fed to the engines inlet to be burnt away without anyone seeing it. Often times the oil is routed through a paper air filter to bugger that up on its way also. These 'cleaner ' engines, clean like those that dilute their exhaust with clean air to reduce the CO2 content of the exhaust. (note reduce the % not the total) now run their chains dry.. So having paid extra to have a bike that does not leak oil you now need to pay again in order to buy an oil leak to protect your chains. just seems daft to me, but then I never understood why something so unreliable as windows sells.

just my two groats worth.

Made my own chain oiler out of a hotel small shampoo bottle, 2 small hozelock valves, clear tube and an inline tube connector + a couple of cable ties, total cost £2.50. The only oil I use in used engine oil! It works a treat.

Regarding desert riding, I always ride with the chain dry, far less wear that having sand and oil griding away at your chain and sprockets!

Cheers