Tamron has been rumored to introduce a new line of mirrorless lenses for Nikon Z-mount for a while – the last video where a Tamron rep confirmed the Z-mount lenses got removed from YouTube a few hours after my post was published.
Here is another concept from a reader for a Tamron 70-180mm f/2.8 mirrorless lens for Nikon Z-mount based on the current Sony E-mount version: