Keep the actual epubs and search in those? (You basically want a transcript of a read out book…which is the book itself.)

https://github.com/qarmin/czkawka

You can try the google trick for RSS if you want to follow an account which does not need login, for example: https://news.google.com/rss/search?q=site:twitter.com/elonmusk+when:7d

Don’t let it out onto the net…

You can try for linux: https://hub.docker.com/r/tessypowder/backblaze-personal-wine

Here is a controversial thought; do you need to replace the 4?

Then use the same password for both for the sake of convenience.

Just copy to the reader?