Is 2560x1080 sharp enough on a 34-inch screen?

It is usable for office work and video, but pixel density is low for this size, so text looks less crisp than on a 1440p ultrawide. If you read a lot of small text, a higher-resolution panel is the better pick.

Can I use it for gaming?

Casually, yes. The 75Hz refresh and 5ms response time handle slower games fine, but fast shooters will show motion blur and the low resolution limits detail.

Does it have built-in speakers?

Yes. It has integrated speakers, which is enough for calls and casual video, though a separate speaker set sounds better for music and films.

Can I mount it on an arm or wall?

Yes, it is VESA compatible. That is worth using, since the included stand does not adjust for height, swivel or pivot.

It accepts HDR signals, but with a 1000:1 contrast ratio and no local dimming the effect is subtle rather than a true HDR experience.

What connections does it have?

It offers standard HDMI and DisplayPort inputs, but no USB-C, Ethernet or daisy-chaining, so laptop users will need their own adapter for video over USB-C.