Hruggek is of course mentioned in many FR products over the years as the chief deity of the bugbears.
Khurgorbaeyag is mentioned as "Kuro", the deity of some of the Batiri goblins of Chult, who are described starting on page 49 of the 2e accessory The Jungles of Chult. That Khurgorbaeyag and Kuro are equivalent is confirmed in the Thard Harr entry in the 2e accessory Demihuman Deities, on page 85.
Nomog-Gaeya is definitely worshiped by the hobgoblins of the FR setting. Page 88 of the Tethyr book from the 2e boxed set Lands of Intrigue describes the massive statue of Nomog-Gaeya set up by ancient hobgoblins which was later partially toppled by humans who defeated those hobgoblins. The location of the now-broken statue is now known as the Gorge of the Fallen Idol.
Beyond that, the remaining goblinoid deities are so obscure that I doubt they have been mentioned anywhere other than the old 2e Monster Mythology, which was setting-neutral. I was hugely surprised that anyone even remembered them in order to have them updated in VGtM! They certainly aren't Greyhawk standouts...
Beyond all that, as others have said, it's a bit surprising that you expected an accessory that was going to be fully immersed in the setting. It was pretty much what I expected, being a fairly setting-neutral book with a relatively decent amount of FR flavoring, which, while nice, could easily be reskinned for any campaign. I do agree that it is odd they abandoned the setting's history for the yuan-ti. but that's a fairly minor quibble.