In the beginning, enthusiast keyboards in the US tended to be Model Ms and vintage/scavenged stuff (AT101W, Focus 2001, Northgate). I came here looking for a USB->SDL cable for a bog-standard 1391401 in like 2009.
The market in Korea feels like it was a few years ahead for a while. OTD and KBMania forums were really where you started to see the dawn of full-custom boards. A lot of these had much more restrictive controllers or were PS/2 based, so you didn't have as much of a software ecosystem, but there was plenty of won being thrown at fancy pieces of milled aluminium.
People interested in HHKB/Topre or Filco products would order them from Japanese distributors-- as I recall some of the earliest dealers for the US market (Elite Keyboards, for example) stocked a lot of this stuff until the market was mature. There were a few caches of other things-- weird boards like the Solidtek ASK-6600U (super-cheap Alps), some Qtronix boards (MX Blue but usually with compromise layouts/build quality), or vendors who'd have back-stock of stuff like Wang 724s (nice-build Alps), which would feed the market for a while. Occasionally you'd see a small feeding frenzy on such things.
The Cherry platform was sort of rocky early on: for a long time, the de facto MX Blue board was the G80-3000LSCRC, which had odd legends and was seemingly available mostly from POS-centric dealers. You'd see people buying various POS G80s for keycaps. A Dolch 1800 was a huge prize because it was one of the rare sources for attractive keycaps.
Some of the more interesting early boards:
Early model G80-86410s ("Ricercar SPOS") which were built with MX Brown, while later production runs went rubber dome. An early feeding frenzy when they sold for like $25. By the time Cherry actually brought out a hobbyist product, they had been lapped by the rest of the industry.
The ABS M1. They had the right concept-- use the Costar CST-104 style chassis (as used on the Filco and CoolerMaster boards of the day) and stock it in a mainstream dealer (Newegg). They then proceeded to blow it up badly-- failing to meet NKRO expectations and building it with Black Alps (at that point, demand for tactile switches was far lower) so they flogged it progressively cheaper to unload it.
Soarer's Converter was a world-breaking innovation. Suddenly there was a USB converter that was reliable and dirt-cheap, but his expansion to a full controller firmware was less of a paradigm shift. It feels like TMK (and then QMK) were what really made full-custom PCBs a real thing.
The first major Group Buy was a very simple Signature Plastics run, with relatively limited options. DCS profile, sort of Dolchish colour scheme, with legends sort of mix-and-match. I recall it was something like $50 for a 104 ANSI set, which seemed a lot of money at the time. It later got retconned as "Round One" in a chain of group buys that went to like Round 6 or 7 with growing ambition and scope here and on Deskthority.
When Ducky first came out, I ordered a 1008XM (Alpsalike) and a 1008 (MX Blue) from Taiwanese dealers. The 1008XM was super-flimsy (the case stripped its screw holes in like one opening and you could bend the plate with one hand) and the 1008 I left with a co-worker as a parting gift. I can recall getting 'Cream Cheese and Green' DCS keycaps for it, and that was about the point where group buys started to explode to the point where you wouldn't follow them all.
I seem to recall the Geekhack/Deskthority split being originally a bit of a US/EU thing-- the base is still much more European over there, but they've developed a much different culture there now. GH is much more "new thing to buy" and DT is much more "old thing to study".
