There is at least one other multiple-CM4 board 'in development', though I can't share any detail, other than keep an eye on this page for when it might appear:

There is at least one other multiple-CM4 board 'in development', though I can't share any detail, other than keep an eye on this page for when it might appear: https://pipci.jeffgeerling.com/boards_cm https://pipci.jeffgeerling.com/boards_cm