I have a couple of zooms… The H4 and the newer version of it… I have not yet tried either as an external USB mic tho. Good to hear it can work with Linux tho.
Is expensive… But if u can find a zoom h4 on ebay, it works as a multitrack recorder with no latency (in case you want to make music recordings with overdubbing etc)… Plus has built in effects and distortion and reverb etc. (when used in stand alone mode, not as a USB sound capture device.
The microphones are phenomenal quality… It can mount on a tripod, and the mics are directional… So as to pick up what you want instead of the sound of a computer or a fan.
If u wanted, I would test out my H4 with Ubuntu for you and see how it works. Even if just to verify that it is a good usb mic.
In stand alone mode, it records at better than cd quality… Without any hiss. And the mic is the best I have owned.
I am imagining that your run of the mill generic USB mic will be kind of like using a phone headset… Maybe not able to get the range of sounds you aim to record?