I absolutely detest this fairly new phenomenon if people listening to loud music or programs on their phones without headphones. No one did it 10 years ago. It's throughly obnoxious.
However, I have discovered a near foolproof way to stop them without having to confront them, which can be off-putting and really, why should you have to.
After being subjected to this numerous times last year - on trains mostly but also in cafes and, memorably, when reading on a sunbed where the woman next to me kept playing Peppa pig at volume 11 to keep her kid entertained while she relaxed.
Anyway, I began to wonder. How would it work if someone near them randomly decided to do the same thing by chance at the same time? Wouldn't that interfere with them hearing their noise? So now, as soon as someone does it, I put sky news on on my phone at equal volume. It creates a terrible cacophony for a minute and then, without fail, they turn theirs down or off. I guess it either shames them into realising how obnoxious they are being or just stops them enjoying the football or whatever it is they are watching. As soon as they do I also have seen enough news and turn mine off.
Massively pass ag but works a treat and suits me as I don't really want to be that person that asks people to turn their phone down and if they take exception and glare at you you can just feign innocence. After all, you're only doing exactly what they're doing themselves.