If you don’t want to do from true/false properties then you can create a collection ( Like types ) and add the three types and create a relationship between users ( Many to One). And then the opposite property will create on the users collection like Type.
Then go to the Signup screen and add the Type property in the form and then a dropdown will appear. Then on the Signup button add a link action to a new screen. You can add a lottie file like loading , A text or whatever like to show loading (If you need) on that new screen. Then create three home screens one for Parent, one for Player and other one for Coach.
And then add three conditional link actions to that created new screen with a lottie. You can add the three actions to the Lottie file after finish or for the screen ( Screen Action).
One link action is Link to the Home screen of Coach if sometimes the Logged in user > Types > Name > is equal to > Coach.
The add the Screen Navigation Type of that screen to Home screen. Then when the user opens the app the loading lottie file will perform and linking to his home screen.
