Purchase a 99 cent greeting card with an envelope.

Carry it with you.
Make sure to enclose a very nicely worded note that lets him know
A. How it's considered very rude.
B. How no one heads off to the coffee shop in the morning in hopes of listening to him on his phone.
C.some people find it offensive.

D. He might be attracting unwanted types of attention .

And ask him to refrain from the behaviour in the future.

Maybe offer to buy him his coffee next week and then politely advise him the his habit is irritating.

If that doesn't work I would suggest getting several friends to join you on Saturday mornings to have coffee and ask, as a group standing around the asshole's table, to kindly change he listening habits.

We were eating breakfast in our favorite Diner and this very large , overly made up Democrat was at the table next to us yacking on the phone while she ate . It was on speaker and annoyingly loud . From the conversation I deduced that the person she was talking to was named Dorothea . Finally I just started staring at her . After a couple of minutes she gave me a " what the fuck are you looking at " kind of response . I told her to " tell Dorothea I said hey ..." OMG if looks could kill . I was dead and buried . She started throwing her shit in her purse and waived the server over to get her check . Sometimes us old folks just don't have any filters .

I was eating breakfast in a diner. not too many people. I'm still eating my breakfast which included over medium eggs. A guy in a table across from me started hacking. Okay, it happens; I didn't pay attention. But he didn't stop at 5 hacks, he was up to a dozen hacks coughing up his phlegm and there I was looking at my runny over medium eggs. H also alternated between hacking and blowing his nose. And I could hear his snot gurgling as he blew his nose while I'm looking at my runny over medium eggs.

So I started hacking loudly too all the while staring at him. Making the sound as if I was trying to hack up a loogie. I think he got my point. But it was too late for me as I couldn't go back to my breakfast. I paid and left, all the while staring at him.

So, yeah, if I were in your shoes, I would watch youtube videos too and maybe he'd get the point as well. I wouldn't even look at him; just pretend I'm so enraptured by what I was watching that I'm oblivious to everyone else just like he is. What's he going to do? Complain that you're playing your video without ear buds, exactly the same thing he's been doing?

It's a coffee shop, and apparently loud, if the management wanted a more library, peace and quiet atmosphere they'd make it that way. I'd rather not risk stuff going sideways with a Bernie Goetz looking dude, risk vs.gain, like I posted about the guy honking his horn in the parking lot as a kid, you don't know what timebomb that is and if he swings a Louisville to communicate his feelings.