Background transparent

My app is scanning qrcode. For this I am using the capacitor-community barcode-scanner plugin. With previous versions of ionic I had no problems; I had used the css to get the transparent background and to be able to see what the camera framed. Now with ionic V6 it no longer works. Anyone who can help me? Thanks so much!

Ionic CLI : 6.17.1
Ionic Framework : @ionic/angular 6.0.5
Capacitor CLI : 3.3.4
@capacitor/android : 3.4.0
@capacitor/core : 3.4.0
Angular CLI 12