Currently the elbows are pointing in vaguely the right direction but they are somewhat off. I have checked that they have the right target bone selected. I have a feeling that this is due to some of the rotations of the bones in edit mode... Can someone help me with this?
I have toyed around with bone roll and it indeed fixes the target positioning, but it also breaks the arm rotation itself. So now the arm is slightly twisted but the IK target is pointed at correctly.
I will have a look at Rigify now. I always thought it was some proprietary addon, but it seems to be part of the engine to some degree...
Yeah, I think you have to unparent, edit the bone roll, and then reparent the model to the armature, but it has been so long now that I don't remember.
And yeah, it does feel like it should be a part of Blender by now but I guess it's simpler to keep it as an addon.
You'll need to adjust the roll of the bones in edit mode. Ctrl+R let's you adjust the roll, and if you have a more complex rig based around parenting thd deform to more advanced control and mechansim bones like ones from the Humane Riggin course, youll want to adjust everything in the mechanism. You'll probably have to go back and forth a few times between edit and pose mode.
Also definitely check out Rigify, it's not some proprietary addon, it's Blender's own rig built into the software. It's really powerful but it's also kind of a lot all at once. There's a lot of resources and tutorials out there that go pretty deep into how rigify works and how all of the setup components can interact. If you van learn how to build out the metarig before generating the full controlled rig, you'll be able to rig damn near anything.