cryptography (not the cryptocurrency-kind)

This may be pedantic, but that is the cryptocurrency kind. The "crypto" in "cryptocurrency" literally comes from the term "cryptography". It is currency that is secured by cryptographic functions.

Most episodes involve some fictional futuristic technology being abused, but that was one of the few episodes that involved only technology that definitely exists today.

• National Anthem
• Waldo Moment (arguable, as it would definitely take some tinkering to set up that kind of Vtuber system, not just using an off-the-shelf system)
• Hang the DJ (arguable, assuming what we are seeing is just a fictionalization of a bunch of software simulations)
• Metalhead (arguable, as robot dogs do not seem quite that advanced yet, but definitely soon)
• Bandersnatch (arguable that the multiple timelines and everything are just the character hallucinating or whatever)
• Smithereens
• Loch Henry
• Mazey Day (though the technology is absolutely contemporary, it does feature a mythological creature or whatever)
• Demon 79 (while it takes place in the past with just old technology, it features supernatural shenanigans again)

EDIT: Fifteen Million Merits is also barely futuristic technology.

From their perspective, it's forever.

cookies are basically given hellish experiences in the only other episode they are referenced

Cookies are featured in several episodes. Not only is the technology slightly different most of the time, it is not always used for torture. In addition to San Junipero, Hang the DJ, Eulogy, and Ashley Too (arguable) are not hellish.

It's clearly "what could happen when someone abuses technology", just like the rest of the series.

What is so dark? I feel like I must be missing something. Their consciousnesses are being maintained by a server farm. But what is dark about that? It just seems optimistic and such how they get to pretend to live in their 20s forever. Nothing like living in a torturous snow globe or whatever.

But you are right, those are definitely outliers. If an episode seems like it is a feel good romp, there is usually some dark existential twist just around the corner.

There are a few that are not.

Got a gallon!

Have the several sequels over the years not suited your fancy?