[2023] The paradox launcher does not find EU4 when I start the game from steam.

You must have run the launcher from the desktop shortcut or Paradox launcher.exe, which is a standalone mode for users who do not want to run Steam. It does need a separate game installation if used that way, but this game was never ported to that platform.

You'll need to run it from the PLAY button in your Steam Library instead.

All the best!