NuclearSpiritMan: I don't want Galaxy to launch all my launchers, I just wanted to know if he could tell me if this or that game needs an update for me to launch the launcher....
I just wanted to know if it's possible to connect to an api that indicates a new update on a game
the problem is, only steam has some kind of API, Uplay, Origin and others does not have any API so you can't check versions.
steam API is not used in galaxy (it uses your login and just parses data that you can see as user - profile data). developer of steam integration explained it in detail on their github in bugs/issues section.
even if gog can go extra mile and query external service like steamdb to see changes in packages it won't help to add this feature to all games (only steam, and after alot of troubles of parsing steamdb webpages).
also gog hardly has any means to see if any game launcher needs an update, so even if they can partly implement this feature for steam games you still will have to update your launchers manually.
that's why I mentioned square wheel. this quest has no satisfactory outcome even if gog will spend weeks working on this.