> When I last looked for this a few years ago, I only found a really primitive one that did a linear transformation of all timestamps in the video, and none to correct each line individually.

Not an answer to your current query, but my first published rust crate shortly after the language hit 1.0 was a tool to both calculate and correct linear drift, long before the era of LLMs or quality audio recognition. It might be fun to tackle this again with the new tech we now have at hand!

Srt-resync: https://github.com/mqudsi/srtresync