Thanks for your quick response, toleda; I will try that and reply later.
[Edit: no effect on "no output devices," but will compile problem report files and include later. (Also, I am not using HDMI anyway, just the sound port on the rear of the Z370N-WIFI board.)]
[Edit 2: Included with my new motherboard is a "Gigabyte" DVD, which although obviously for a Windows computer, also includes a "Realtek" file having a listing of hex numbers (codecs?) plus another batch of data comprising about 729 MB of stuff. Any chance any of that could be useful?]