> On a 34" ultrawide monitor, it was too easy to put YouTube running on the left side

This has zero to do with an ultra-wide monitor and all to do with a lack of self-discipline.

I bought one of the first 38" ultra-wide monitor that came out from LG and, ten years later, I'm still rocking on it every day.

You know what? My main computer doesn't even have sound. You read that correctly. No sound. So no Youtube vids. No games. Not that I'd be tempted: but because I've got actually zero need for sound on that machine.

And I'm no luddite: I've got two servers at home, more in datacenters, countless Pi's, NUCs, and laptops. But on my work machine: it is no sound and a 38" ultra-wide.

If you need to use a monitor the size of a stamp to make sure you can't run youtube vids at the same time you're working, the issue is you, not the monitor.