I know there have been numerous threads in the past regarding this subject, but they end up in an echo chamber kind of situation, where pretty much everyone agrees that using your mobile phone in certain ways is despicable. Obviously that cannot be the case, as there must be a sufficient amount of people out there acting in a way that sparks this outrage in the first place.
So, a) watching videos/reels or listening to music on speakerphone, b) having (video) calls on speakerphone c) talking on the phone either using earphones or "normally" but in a normal to loud voice and more than one minute.
Are you one of the apparently-non-existent-when-it-comes-to-Mumsnet-threads people that exhibit any or all of the abovementioned behaviours out in public? This is your thread and your time to shine. Are you oblivious to the fact that others find it rude? Are you aware, but you think it's normal and that they are pearl-clutching weirdos, so you do it anyway? Do you also find it rude/irritating/inconsiderate, but don't care because reasons?
YABU: It's normal, that's what smartphones are for
YANBU: It's rude and antisocial