>Unfortunately, Android [9.0] suffers from poor user interface design in a few areas, and one of the most annoying flaws in its user interface is simply that the stock Android OS doesn’t have flexible enough options when it comes to controlling when the phone rings, which is one of the most important aspects of a phone.

Do Not Disturb, at the time of Android 9, did support controlling when the phone rings.

>Bedtime mode is quite useful, but I still have the other problem that my mom could decide to randomly call me in the daytime as well, and unfortunately I rarely want to take her phone calls. However, I also don’t want her to end up homeless or in jail (which has happened before, but that’s a story for another time), and so I don’t want to block her and completely lose the ability to receive her calls. This results in me having to almost always have my phone set to “do not disturb”, so that I don’t have to be disturbed at random times by unwanted phone calls

Could he not have used a custom ringtone for his mother?