changing default ringtone??

i’ve noticed that whenever i get an instagram notification, twitch notification, or any similar app that doesn’t have their own sound (like snapchat), it’s ALWAYS tri-tone. i was wondering if this could be changed to something else. even within apple’s choices, i think there are way better choices since i find tri-tone obnoxious and alarming. i want to chose a more calmer ringtone. it doesn’t give me an option to change this “default” ringtone i can change my phone call ringtone, text, mail, calendar, etc. but never this. i hope we get to, in the future change this default ringtone to a different one or even better, chose different ringtones for different apps i would love to have more freedom with my ringtone choices