What about The Sexy Brutale (HNPY)?
If you liked Edith Finch, maybe you should try Virginia, it’s a pretty neat game, but not if you deem clear-cut answers at the end a requirement. It’s inspired by 90s classics, most obviously some of Lynch’s works and X-Files.
All of the Blackwell games are about solving cases, and are under your 8 hours requirement but not particularly challenging. The early games might be looking a little janky by today’s standards.
Some other adventure games: Kathy Rain (another game with 90s influences and Lynch-ian overtones, but a more traditional storytelling experience), Whispers of a Machine (HNPY), Gemini Rue, The Shivah (small adventure by the Blackwell author), The Silent Age (this is more of a SF mystery but might fit your format because of the underlying episodic structure), Agent A: A Puzzle in the Disguise (HNPY), Tales of the Neon Sea (your enjoyment might depend on your tolerance for Engrish), Cognition.
Not exactly an adventure but not too far: Detective Grimoire.
Stuff that may or may not fit the bill: Hacknet (hacking sim with a mystery narrative), Orwell: Ignorance Is Strength (has its own particular brand of detectiving), Heaven’s Vault (longer than 8 hours).
The Darkside Detective if you like that particular brand of humor.
HNPY = have not played (yet)
Batman The Telltale Series.
I’ll see that and raise: Gone Home.
My first thought buy way above the 8 hours mark.