klbr web ships two open fonts, vendored so the tool works offline.
ioskeley/IoskeleyMono-{Regular,Medium,SemiBold}.woff2 Ioskeley Mono (c) Ahatem
https://github.com/ahatem/IoskeleyMono — SIL Open Font License 1.1 (see ioskeley/OFL.txt)
subset to latin + punctuation + arrows with fontTools; ~49 kB per weight.
inter/InterVariable.woff2 Inter (c) The Inter Project Authors
https://github.com/rsms/inter — SIL Open Font License 1.1 (see inter/LICENSE-Inter.txt)
Ioskeley Mono carries data and prose; Inter carries chrome labels and buttons.
Both are taken from the reference site's own stack (git.t4t.associates serves InterVariable and
Ioskeley Mono), which is why the pairing is not a coin flip.