There's a particular variety of black metal I enjoy a great deal lately that's minimal as far as complexity and variation of rhythms but is highly riff-based. I'm looking for material where the guitars are very dominant and play a great deal of riffs, generally variations of each other that really explore the musical space. Here's a couple good reference points:

Absolutus - Ostendit Quam Nihil Sumus - This is really the template of what I want: intricate (but not technical) riffing over a mostly unchanging drumline. The very melodic and memorable yet distinctly dark and minimal riffing is a very good indication of what I'm looking for.

Excessum (Sweden) - Death Redemption - This is a bit more active structurally than Absolutus, but the riffing is so excellent that it's fine. Very intricate and melodic with a depressive atmosphere, and most specifically, the precise variety of riffing that I'm looking for with the same infatuation with slight variations to build atmosphere.

Looking for underground bands and having a similar production to those two (a bit smoky, claustrophobic, and warm) is a plus.

Cradle of Filth - Dusk and Her Embrace album - top notch minimal bm.
You might know them but they are worth checking out a second time in every clime.
BTW, Sam, they are not Norwegian though.

Sargeist's "Satanic Black Devotion" Might be worth checking out for you. Pretty minimal bedroom type project. Solid riffing though, but not over technical by any means. Pretty much standard high (but not blasting) tempo drums straight through the album.

You might want to check out Nyktalgia, especially their self-titled debut. They might be what you have in mind. Wouldn't hurt to give them a try if you haven't listened to them before.

I'm not sure if I can help, but I'll take a stab at it.

I'm sure you've heard Heresi, right? Not technical, but intricately designed, imo.

Myrkr is a band I've been listening to for a while. They have something of a murky production. They are a bit more mid-tempo. However, I think they utilize some fairly decent tremelo riffs.

Another one I almost forgot to mention is Tenebrae in Perpetuum, but I don't find them "warm" at all. Reminds me of riffs that have such a despondent "lacuna" to them. Heavily minimal out of these three.

Of course not, they sound as cold as cold is. I don't think it's what he's searching for, sure it's minimal but there isn't much variations of same riffs or that kind of stuff, just glacial simplistic black metal. Definitely worth listening to though.

I don't know how obvious some of these will be, but just in case:

Some of the current Norwegian bands seem to be very adept in this. Furze, Taake and Kampfar in particular just have some amazing riff-work, without ever becoming too complex or technical.

A perpetual favourite of mine is Algor - Uder Pohanskeho Hnevu. To the point, simple and just great riffs.

I also find Armagedda's last album having very strong riffs, with a nice crunchy production.

Branikald's Stormheit. It's very different from any other BBH release in that it has far more variation and character in its riffs than the near ambient material of later albums, draped over practically unchanging drum-lines.

End from Greece takes after Carpathian Forest, but utterly kicks the shit out of them in the quality department. Wish they had made more than two albums.

Closer to (my) home is Fluisterwoud, which is one of those bands that emulates "A Blaze..." while understanding what makes that album good, so simple but not stupid songstructures and infectious riffs up the wazoo.

I got the impression from somewhere that you like Legion of Doom You might want to check out the recent reissue of Wolfnacht's first album Heidentum which hits a similar vibe. It also has the better songs from the second album and last demo on it, remastered so the vocals don't bury the actual music, so it's quite nice.

Finally, Nehemah's debut and the German Pest's second album might be up your alley.

Noktorn, have you listened to Furze at all? I think Trident Autocrat might fit the bill here, but I genuinely don't remember how active the drumming is at the moment. There are some very interesting twisty-turny (and sometimes just straight up bang your fucking head) riffs but not a lot else going on aside from the bass which is audible.

I'm not familiar with your examples but I figured it didn't hurt to take a stab at it. Let me know if it's anywhere near what you're looking for.