Rashi's commentary on Line 21 as as follows:
have provoked my jealousy: They kindled My anger.
with a non-god: With something that is not a god.
with a non-people: With a nation that has no name, as Scripture states, “This land of the Chaldeans-this people was not” (Isa. 23:13). And regarding Esau, Scripture states, “You are very despised” (Obad. 1:2).
I will… provoke their anger with a foolish nation: These are the heretics. So Scripture states,“The fool (נָבָל) said in his heart, There is no God!” (Ps. 14:1). - [Sifrei 32: 21]