Lastly, I grabbed Immortal - At The Heart of Winter for 50 cents at a flea market; a bit blind, but I knew it was black metal due to the picture of the band on the back of the album cover. Turns out its a damn good record; almost thrashy, even.

It's probably their overall best record by a solid distance IMO and indeed they are now known more as a black-thrash band due to what they've been since the ATHOW era. They transitioned to a 2-piece (lost the long-term guitarist to an elbow injury) and went to Tagtren's Abyss studios for this album, and generally were at the peak of their inventiveness like a lot of bands of this era and cluster of metal, again IMO. Every track is a minor masterpiece, I have a ton of gnostalgia wrapped up in that album.

Speaking of black-thrash, I'm still listening to to the 2021 self-titled from the reincarnated Absu aka Proscriptor McGovern's Apsu which I waxed slightly over-earnestly about in this thread. Went and double-dipped on a picturedisc purchase despite it being my only ever vinyl buy and having no way to spin that copy atm. I wouldn't call them black-thrash any more - a lot of death influence has crept in, so they're like a progressive black-thrash-death extreme metal multitool now - but they were the undisputed kings of black-thrash for their albums spanning 1995-2001. Anyway the new one has been carrying me all year - great shit and you might like it, since although it could never be considered mathcore or whatever, it has some of the angular, challenging experimental elements which I identify as similar to some of the bands you listed.