Allowing alarms to sound during calling states ( phone / skype / Discord )
There's an app called AMdroid that let's me do it. Very late answer but eh. You have to go into the setting and to the global settings and "in-laws behavior" there's an option for ringing while on call you just have to let the app have permission to do it. Hope that helps

Play Link: https://play.google.com/store/apps/details?id=com.amdroidalarmclock.amdroid