The entire app is meant to be LTR not RTL, so I think you're going to have difficulties, but here's what you can try:
1. Switch the application language t a RTL one.
2. create a file called init-custom.php and place this code in it to activate RTL:
Next, your problem would be how various elements display here and there, but that can be fixed with custom css, so create a file called style-custom.css and place it in /backend/assets/css then in /customer/assets/css and in /frontend/assets/css where yo can place your modifications for each of these sub-apps.