How do I make my Galaxy A13 screen stay on during speakerphone calls?

[HarryC]

I often prefer to use the speakerphone feature when making calls on my Galaxy A13, with the dialpad screen on to select choices etc. I've tried 'screen stay on' apps which do work for the phone in general, but none seem to work for the phone call screen. It always dims after ten seconds and goes off after 30 seconds. Am I missing something?