Creative director/tester for a board here.
I got the game set up (works perfectly with wine and firejail on Linux, no steam. As a very casual gamer, I'm amazed by this timeline)
For idiots like me wondering how to start an AI only match because the damn controller won't go in the middle, you Play Match, start an Exhibition Match, select the teams and then when the pre-match settings show up, click (Y) for Coach mode (the 'w' key on my keyboard) and a manager's icon appears. This will give you control over your team's formations and subs but the AI play each other on their own.
If this is improper advice, please correct me.