Junction box partially behind drywall and partially exposed
You can certainly do it with a junction box (in the wall) an an extension ring (out of the wall.) I don't know if there's anything against using a deep box halfway out of the wall as you suggest or not.
If a sweep fits, an LB will do - or if you don't actually need a pull point there, an offset through the surface of the wall will also do. Just make sure it adds up to less than 360° in bends between pull points. i.e. you are in conduit on both side of the drywall surface, there's no transition. You need a box if it's cable on one part and conduit on the other - if it's all conduit, bring it through the wall, mud and paint the wall around the conduit penetration (or use fireblock foam/caulk if the wall requires, or a fancy fire collar if the LAHJ insists) and keep going.