Double controller/controller connecting problem
Unfortunately after about 4 hours of trying literally everything I came to the conclusion EA's way of supporting Steam input is broken and following some reddit posts and tickets on these forums it seems like this is an issue that already exists for at least 7/8 months now and clearly not only in FC26 but also previous titles, EA please for the sake of everyone's sanity produce a working product before release.
The problem is with controller support. When I enable Steam input it doesn't override the EA input. This makes it so controllers are being duplicated when registering input. Since it registers twice every input you give is also given two times and therefore the game is unplayable. For some reason this problem currently only affects the first or a selective controller and not specifically all controllers.
When I try to add a second controller through steam input this is doing fine but my first controller is still not working. When I try to use EA input registering and fully disable Steam input it will register the first controller without any problem. The second controller on the other hand is not getting registered in this case. So not only is the Steam approach broken but also the EA approach.
The one thing that makes it the perfect bug is that this doesn't always happen. It happens around 90% of the time. There only is this small possibility of the game actually functioning as "normal" software. The only solution I have found is restarting the game about 20/30 times and by then it would give me a startup that actually works.
The things I have tried to solve the problem:
Restarted the game.
Deleted and reinstalled the game.
Turned off all overlays.
Disconnected all other connected devices.
Enabled/disabled Steam input.
Used a different controller.
Changed screen settings (V-Sync, fullscreen, etc).
Closing every application active.
Using different USB/Bluetooth.
Updated firmware/drivers.
This also isn't a problem in any other games. Games like Rocket league, Forza horizon, The crew, etc and it works no problem out of the box.
Least playable Steam game to date imo.