As stated earlier by AliasNull.....The issue is a reproducible software bug within the EA Javelin Anti-Cheat's game detection and service registration process for the Steam build, not a user-side configuration error.
After much testing he concludes.....The issue is a definitive software bug that prevents Battlefield 6 from launching. The evidence conclusively demonstrates that the EA Javelin Anti-Cheat installer fails to detect the Steam version of the game on certain hardware configurations, leading to a broken service registration that cannot be fixed by the user. Even when the service is manually and correctly installed, the main game executable still crashes immediately after the anti-cheat driver is loaded.
There's a clash between EA Javelin AntiCheat and newer Insider builds of Windows 11 (24H2 and 25H2). So nothing to do with our side, it's all on EA to update Javelin AntiCheat. Why can't they make this a 'known issue' so everyone can stop doing all sorts & wait for a patch/fix.