I was able to change the incoming email address through Project Settings > Channels > Customer Permission > "change the Global settings." however this only lets me choose the incoming one, not the outgoing one.
But it seems to be outdated or something as there is no "Settings" Option and neither is there a "Summary" option.
I hope someone can help me as I've wasted the past 2 hours trying to figure this out.
Welcome to Atlassian Community!
Checking the details you provided, I believe that you are using a next-gen project, that's why you can't find the option mentioned in the documentation.
To confirm if it's a next-gen, go to your project and on the bottom left you will see the information:
If it's indeed a next-gen, then we must wait for the feature to be implemented:
Click on vote and watch for the above feature to receive future updates.
If it's not a next-gen, then you can change the email by going to Project settings > Notifications.