From what I have read on the magnetic reed and the hall-effect is that the vast majority of them were of linear feel.
Most hall effects are linear (very much so) but I did find one clicky hall effect (honeywell / microswitch) keyboard, the clicky was nothing special, and widely variable. Reeds are mostly linear, but you can hear (and feel, a little) the reed closing at actuation. It's pretty cool, but still basically linear.
Bytheway, there are a ton of reed KB's on eBay all the time. Keytronic-made magnetic reeds were very common and popular for a long while. There's some for as low as about $30 shipped last time I checked. The manufacturer has since switched to cortron inc.
60% Ms and Fs do exist, but not in the HHKB layout. Wcass made a custom 60% M, which might be able to be tweaked to be in the HHKB layout, and the 6019284 keyboard (Kishsaver) is a stock 60% IBM Model F.
60% stock M's exist. Clickclack has one. It's supposedly from a label making machine. Very rare though. Just wanted to add the specific example to your post as an alternative to DIY efforts. Hasu has also made a 60% m, and was possibly the first to do so.
I want this:
Show Image
Except left-hand TK and modern ANSI layout. I haven't tried enough switches yet, so far I'd say Browns or Pink Alps.
There's a good chance that KB uses hall effect (ferrite type) switches.
I really want a keyboard with MX greys.
Pretty easy to just make.
I use a bunch of different layouts, but I'm particularly fond of ones with tenkeys. Different keyboards and switches have different purposes, feelings, and drawbacks.
That said, my #1 keyboard that has been made is the IBM 4704-400 "administrative" 107-key keyboard, Part number (for US language) is 6020218. These used to exist at a place in Texas, but were since scrapped.