Lunr.js isn't really being developed anymore from what I remember. I switched from Lunr.js to SQLite FTS in browser myself. I'm using sqlite-wasm-http [0], which uses range requests to only pull relevant pages of the static database as needed. Though if your search query is short enough, it'll probably pull the entire FTS table anyways.

[0] https://github.com/mmomtchev/sqlite-wasm-http