Now I just need some kind of open source search engine to run on it ... (a bunch of text files that render to HTML, and ideally following the links 1 or 2 levels deep)
~20 years ago Google desktop search was a fantastic piece of software ... very fast and accurate on your local files. I don't think something like that exists now, and maybe never existed for Linux
Search engines are extremely modular and Unix-y. You have a bunch of indexed corpora and you intermingle them at ranking time, with respect to a query. But unfortunately there is no real incentive to provide something that has measurably good results and is also open to your own data and modifications
The incentive is to make a walled garden out of it
State of desktop search is very bad but this is what I use. It is of acceptable quality.
Here you go: https://yacy.net
And if I may expand a little, not just for crappy Google, I also create alternative local knowledge bases at work.
I can't find anything at work. Everything is spread out across chat, Wikis, SharePoint, email. All having different owners, content may at any time disappear or move, there's constant authorization headaches.
Whenever I come across something useful that I expect to be of some future use, I make a local copy. File, web page, wiki, anything. Because our information systems are a massive failure.