Here is a very simple leg.
Leg.lower.L has an ik constraint applied, of chain length 2.
Foot.L has no ik applied but copies its rotation from IK_Foot.L
As discussed here here this enables the Inverse Kinematics fields of Leg.lower.L & Leg.upper.L
I want to limit the rotations of the upper leg hat may be caused by ik. To test the extreme case, suppose I attempt to prohibit rotations of Leg.upper.L completely. I have applied Lock IK for X, Y & Z.
However, as you can see, those locks are ignored.
Why are the locks having no effect?
Blender v2.83.0 on Linux