Perfect Chess Database - Apps on Google Play

ChessBase 15: The new fast reference search

How to install OM

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

ChessX Flathub

Small Encyclopedia of Chess Openings ABCDE on CD (3rd Edition)

ICCF

How do I switch from Masters database to Player database for opening explorer? - Chess Forums

STE Club- Chess Tutor

Does the win/draw/loss rate from the opening database also apply to lower rated games? - Chess Forums

Databases: Tips, Tricks, and Softwares