@IndexLibrorum Hi, it definitely was the browser.
Cleaned everything (unistall faf and sc:fa), deleted folder is user and roaming, changed defaunt browser to chrome, reboot, reinstall sc:fa, launch a skirmish, install faf -> done

@IndexLibrorum Hi, thanks for the reply but could you be more specific by "correctly using" ?
Installation process : next next next all in default location, finish.
When I double clic the desktop shortcut I get the very same image from OP.
A screen with a few buttons bu nothing happens when clicking "connection" (blue button) and no fileds to enter my username or password.
Will try discord, thx for the tip.

Hello, just installed the game again since it was on sale on steam this weekend. Launched the game, created a profile and a skirmish, quit, installed FAF.
There are no fields to enter my login and password, also no option regarding the game install folder.
Dods someone has a fix for this ?
Running Windows 10 latest update