As much as the Tenere' appeals (I wish we could get them here in the US!)
given what Trich has said, it's got to be the much lighter weight and much less expensive XT for a first Africa run.

Why not find a low miles used one that is already set up for travel? Don't get suckered into hard panniers however. Biggest amateur mistake. Go soft bags, keep it cheap and simple but find a bike that has been gone through and has skid
plate, bark busters, rack of some kind, case guards perhaps, big tank, nice seat (important!!) proper tires and perhaps a nice box of spares.

You won't find many Tenere's set up this way but XT's are much more common.

The Tenere' weight is massive for a single. Go weigh one, you won't believe it. It's got to be 30 kgs. heavier than a standard XT. If you are a novice off road rider this will really hurt you and could be quite discouraging.

By the time you've added all the bags and tools and camping gear, you've added a lot of weight to any bike. So starting off light is best.

The Tenere' would work for more experienced off road riders or those not doing any rough going.

As far as theft goes, not such an issue in Africa from what I've read of reports here. I've only done Morocco, no problems at all outside cities.
You just need to find a place for the bike. Not too hard most places.