UXN was developed out of necessity , because some software stopped working in certain environments. AFAIK author is living on a boat. and doesn't have unlimited electricity and internet access. Their electricity supply depends on weather.
When you look at it like that, information security is largely first world country problem. whilst 3rd world country is happy if it has internet and electricity at all.
You're right, OpenBSD with something like Dillo or NetSurf might go a very long way. I'm not sure though if I want to run OpenBSD on the TiBook, I have plenty of more powerful hardware for that, and running a modern, portable OS removes from the flavor of such retro hardware - e.g. it's the most modern/powerful laptop that can still run OS9. There still are people who maintain and write new software for the classic Macs (one of them, jcs, being an OpenBSD developer). I'll have to explore my options more thoroughly here, but either way, that machine struggles even with modern SSH, something you're used to being instant.