The Asus Maximus VIII Gene is the current overall Z170 mATX flagship mobo, and is priced about $75 higher than Gigabyte's mATX version mobo.
Maybe when the Intel Alpine Ridge controller becomes more widely available to brands other than Gigabyte, we'll begin to see newer mobo options.
AFAIK, SuperMicro offers the only mATX Z170 board that includes these 3 on-board video port options: DVI, Display Port, and HDMI 1.4.
Inclusion of an Alpine Ridge controller would enable HDMI 2.0 (in addition to Thunderbolt), if any mATX board maker would get around to producing one.
So: if an Alpine Ridge controller were actually present, you'd also have an HDMI 2.0 video port listed in the mobo specifications.