Has anyone SEEN the Father?

Genesis tells us that YHWH appeared to Abraham - he SAW him (in addition to two others with YHWH). Yet, the Gospel of John says NO ONE has [ever] seen God.

"YHWH appeared to him [Abraham] by the oaks of Mamre, as he sat at the door of his tent in the heat of the day."

- Gen 18:1

"No one has ever seen God"

- John 1:18

"not that anyone has seen the Father"

- John 6:46

John makes it clear it in that verse that only those who have seen JESUS has seen the Father (God).

"except he who is from God; he has seen the Father."

- John 6:46

Jesus himself makes this clear;

"Whoever has seen me has seen the Father"

- John 14:9

This begs the question; Who exactly appeared to Abraham?

I'd love to hear your thoughts.