Mossberg makes a few nice 20 gauge models suitable for home D. Not sure I agree with the author about lack of industry support.
I had a Mossberg 20 gauge with a pistol grip and 20 inch barrel for home defense, but it fell out my boat, along with several other weapons...worst day of fishing ever.
I have no trouble purchasing shells and slugs for my 20 gauge.
Mossberg says that my HS-410 will/can use Slugs and any other loads. It fits well for indoors and close range.