[Kolokotronis]

"What “heresy” would that be?" A fundamental denial of the truth that the Father is ΅Ο ΩΝ", the Being Which created beingness. The Rublev icon does not purport to depict the Father (or the Son or the Holy Spirit for that matter), rather it is a depiction of an ancient scriptural pre-figuring of the Trinity.

[Claud]

There is no such denial in the depiction, any more than there was in the “Hand of God.”

And I beg to differ that the Rublev icon doesn’t depict the Father, at least that’s not what the article says:

“...they chose to use Andrei Rublev’s Trinity icon as the proper way to depict the Father, Son and Holy Spirit......The first angel wears a blue undergarment, symbolizing the divine nature of God and a purple outer garment, pointing to the Father’s kingship.”

On the other hand, this article below makes some good points (particularly about the Son being the representation of the Father). It ends though with a bit of a fuzzy conclusion about the propriety of such icons:

https://blogs.ancientfaith.com/orthodoxyandheterodoxy/2014/09/08/show-us-the-father-how-the-father-may-or-may-not-be-depicted-in-orthodox-iconography/

I would be inclined to view the Russian declaration on this as a valuable stream of thought but not (without an ecumenical council) binding on the entire Christian world.