The BT spec defines 5 overly complicated ways to do any given thing but most devices only support 1 or 2. Multiply by the number of things that need to be done.

The BT spec defines 5 overly complicated ways to do any given thing but most devices only support 1 or 2. Multiply by the number of things that need to be done. In practice the compatibility situation is "test all pairs" and just as bad as if there were no standard at all.