It's not a transfer. If a trust owns a game, then the trust owns the game. A transfer of trust is not a transfer of ownership of the trust's property.

Now, moving a steam account into a trust might be a breach, if they care. Even using a trust to buy a game might also be a violation of some form, perhaps, buried in the toc.

But the trust itself is a legal entity and it can own things. Just because the people behind the trust changes doesn't mean it was a transfer on the public side of the trust.

The trust won't own the game.

> Now, moving a steam account into a trust might be a breach

Morever, it can't happen. Accounts are non-transferrable.

> Even using a trust to buy a game might also be a violation of some form, perhaps, buried in the toc.

Right at the top, actually. GOG, not Steam: "This license is for your personal use."