What if islam, in very clear terms, bans all kinds of slavery? It strikes me as a good way to get more technological progress according to the usual arguments. On the other hand, it might be a bad selling point at times.
Islam does prohibit slaves, sort of. It prohibits Moslems from holding other Moslems as slaves, C.S. Forester, The Barbary Pirates, 1953. However,
it didn't prevent them from holding non-Moslems as slaves. The same source.
Islam also prohibits holding Christians and Jews as slaves, unless captured in warfare (you can't enslave any "people of the book" that have submitted - but conversion is not necessary).
There were loopholes created, like for the Jannisaries.