Regarding Javelin, I tried repairing and reinstalling the game, but neither fixed the issue. I also tried uninstalling the game and reinstalling it through the EA launcher. Now, it crashes immediately after the “Respawn Entertainment - Electronic Arts” splash screen, without displaying any error message. Also did the repairing of Javelin itself but didn't work either.
As for the troubleshooting guide, I don't have any background tasks running that could interfere with the game, and the options listed after that don't apply to my situation. Neither are open applications that could potentially be causing errors, as the only things running are Apex (on infinite load screen), Spotify and/or Edge
Update: I've finally get to pass through the loading screen. Apparently it only launches correctly if Apex is the only program running in the moment of launching (not so fun having to close everything just to open the game and then re-open all other programs as Spotify, Youtube, even other games to play while looking for match)