I got one of these $30 pi clones and audio works but there is no ttyUSB. The cp210 is enumerated on USB. I guess there are no VCP drivers and not sure any of the ones on Silabs site would be possible to use.
I may be mistaking, but my understanding is that the driver availability is dependent on the architecture and OS you plan to use, not so much directly the hardware. If what you got is a remotely accurate clone, it should have the same CPU architecture as RPi and you can run the same Linux flavors.
CP210x drivers including Linux version are at: