Datasette is proving a surprisingly good replacement for Recoll as a personal search tool. I wrote a somewhat terrible Python script to dump my videos folder's metadata and subtitles into SQLite for it. I haven't worked out how to remove/transform columns from/in the default view nicely yet though. Maybe it would make sense to literally just use an SQLite VIEW.
It looks like autotranscribing the unsubtitled stuff will take several days of compute time, which is not great.