ChessX Flathub

Chess Openings and Book Moves

Chess Openings Chess Opening Software

Chess engines vs. chess databases. Which one to use?

learning - Where can I find free training tools like detailed annotated chess openings, middle games and endgames in the PGN format? - Chess Stack Exchange

Build your Chess Database –

Chess database searches for annotated games (ChessBase Tip #0004)

ChessX is an Open Source chess database - new version 1.1.0

All 1d6 Opening Repertoire Collection (6 Digital DVDs)

How to use a Chess Database to Improve your Openings

How To Use The Opening Explorer - by Nate Solon