Unfortunately, there is no concrete solution, other than Silent Mode, or activating Do Not Disturb if you have a call where you do not want to be disturbed. I tried to check if it was possible to set up an automation that would automatically activate Do Not Disturb during a call, and deactivate it when the call was over, but this is unfortunately not possible.
Alternatively, but probably not as interesting. If there are one or more apps that particularly disturb you when you have phone calls, you can customize the notifications so that the specific apps have no sound.
Go to:
Settings > Notifications > select an app > disable Sounds