

It seems to me that the offending dialog would only be triggered if you did a full fresh install. During the previous iteration of the testing, they probably had a VM somewhere with it installed; since the underlying packages were already present, the dialog would never have popped up.
I would assume that they left the MX off of laptop GPUs, since they’re all MX cards, until recently. Regardless, the “card of the right approximate era” thing should work, unless there are specific patches for your card, which is unlikely.