"Hebrews 6:18 ...it is impossible for God to lie...
It's true that God cannot lie not that He will not. It's not because it's IN His nature not to lie, it's becasue it IS His nature. God is Truth. That is why He cannot lie."
If this is taken literally.
If there is anything that God CANNOT do, He is not God, but simply an immensely powerful being.
God does not lie, because He does not choose to lie, nor need to lie. (Lie to whom anyway?)
An immensely powerful but limited being, limited by anything, is not God - by definition - and not interesting.
"An immensely powerful but limited being, limited by anything, is not God - by definition - and not interesting."
IIThessalonians 2:3 And for this cause God shall send them strong delusion, that they should believe a lie:
Sound powerful enough.