According to [Stable Update] 2020-11-27 - Kernels, Browsers, Maui-Apps, Pamac 10.0-Beta, Gnome, Mesa, Qt, 5.7 is in end of life as well, so I switched to 5.9 and now it works without any problem; thank you, wouldn’t have thought of that.
For the record, PulseAudio showed (and shows) “Headphones (unplugged)” when they are unplugged and just “Headphones” when they aren’t.