Yes, I think the author is making a good choice here. Forth is indeed very well suited for these specific constraints. There’s a reason why it was popular on very limited machines such as the Sinclair ZX81 (see Husband Forth). The Jupiter Ace even had Forth in ROM, instead of BASIC as was common at the time.
Now we just need a collapse computer to go with it.
As far as I can tell, the RC2014 is the “flagship device” for collapseOS: https://rc2014.co.uk/
You can hand-assemble it using thru-hole soldering only.
Still too supply-chainy. Z80 through-hole chips are sort of a boutique item. Wouldn’t be surprised if most of the inventory out there is surplus from 20 years ago. If existing inventory survives the event, x86_64, ARM, and existing OSes would be the most probable survivors.
It would be cool if there were something we could fabricate using near-ubiquitous technology and materials. Maybe some kind of laser-printer based lithography process? Like inkjet t-shirt iron-ons, but for integrated circuits.