The recent Ghosts series by Nine Inch Nails is ambient in a dark and atmospheric sort of way. The latest volumes (V & VI) are available for free here (and probably on your streaming service of choice).
Big ambient fan since early 90s. Especially stripped back techno variants.
Favourites by a mile:
David Sylvian & Holger Czukay – Flux and Mutability
Orb – Live 93
The Orb – Orbvus Terrarvm
FFWD – FFWD (rare but still on youtube as of last look)
Gas – Zauberberg
Gas – Königsforst
Gas – Pop
Marsen Jules – BeautyFear
Helios -Moiety
Markus Guentner – Shadows Of The City
There are a few more that escape me, will have a look in my playlist.
I’d say ‘Dub Side Of The Moon’, but DSOTM always made me well up and threaten to break down into a big blub. Most melancholic album I can think of, even the upbeat dub version ymmv