re: Stoner Metal/Sludge/Doom/Post-metal/Blues Rock/Psychedelia

No. It definitely is not the debut Black Sabbath album. I've been playing some songs from that album, and, it uses standard tuning for guitar with no special fuzz, distortion or other guitar pedal effects.

The debut album can be described as "heavy blues".

The third album is Master of Reality. I've played some songs from that album on guitar. The bass and guitar are both tuned to C sharp, which is three steps below standard tuning -- that had never been done before on a rock record.

Tony Iommi says that he used that tuning to get a heavier sound, and it worked. Tony uses his classic guitar pedal effects on Master of Reality.

I've been listening to and playing songs from both of these albums for some time now. The opinion of rock music at large installs Master of Reality as a seminal catalyst for the birth of Doom Metal/Stoner/Sludge Metal.

A good listen of the song "Into the Void" bears this out.

LINK

The heavy, sludgy and long intro are pure Sludge Metal. The doom and gloom lyrics are pure Doom Metal.

Lots of rock critics consider the debut album as the first "Heavy Metal" record, but, HM is not the same as Sludge Metal/Doom Metal.