Here's a game that might fit the Game Dungeon: Drowned God: Conspiracy for the Ages.
It's a first-person Sci-fi adventure game with a gorgeous pre-rendered 90's aesthetic. The game delves into a massive assortment of conspiracies mainly focusing on the deliberate manipulation of history, also including alien intervention, the Knights Templar, and government cover-ups. It was actually a Windows 95 best seller in the fall of '96, but the bugs in the initial version and outright strange and occultist themes and imagery hindered its sales and shoved it into obscurity.
The real mystery behind this game is the unhinged developer, Harry Horse. He was an English author, illustrator, political cartoonist, conspiracy theorist, and former lead singer of the psychobilly band Swamptrash. According to Harry, Drowned God was based on a forged manuscript, claimed to have been written by 19th-century poet Richard Henry Horne.
I'll quote Wikipedia directly regarding the sequel to this game:
I think this would be a prime candidate for the Game Dungeon considering that it's an obscure and bizarre sci-fi adventure game revolving around conspiracies developed by a questionably mentally stable individual. Although, I have heard that the game can be dim and depressing, the puzzles can be frustrating, and the game might be cursed, but the content might outweigh those aspects.
Drowned God is abandonware, so it's freely available here, complete with a manual, guide, and patches:
https://www.myabandonware.com/game/drowned-god-conspiracy-of-the-ages-bel
As far as how easy it is to get running on modern systems, that might be a bit of a challenge, as I haven't had much success running it on 64-bit Windows 7. But considering how incredibly hostile Armed & Delirious was, this might be nothing compared to that game.