Hi!
Unknown interface but with some googling I found that sb2000 mk2 has 2 serial ports done with FT2232 chip.
That chip is "multimode" one that perhaps needs its own drivers (that is unusual in linux world).

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http://www.cgantenna.be/product_sb2000mk.html

Now we release the new update SB-2000 MK2 USB radio interface. It uses new FT2232 chip to support 2 serial ports.

2.USB to UART bridge by FT2232 single chip. USB 2.0 compliant. Full speed.
To be compatible with the legacy radio program, we still have to keep using serial port. That's why we choose to use USB to UART bridge which converts the USB to serial port. The new FT2232 supports 2 serial ports. Therefore user could use 1 port for rig control and another port for digital operation.

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Disconnect sb2000.
Open console and give:
ls -l /dev/ttyU*

Note resuts.
Connect sb2000.
repeat
ls -l /dev/ttyU*

Did any new devices appear? Referring to above there should be 2 new ttyUSBx devices.

If not it seems that kernel does not support chip by default. Use Google to find drivers for ft2232 chip.
Put words:
ft2232 linux
to google search and study results.

If your sb2000 is not "mk2" then it might have something even more special inside.

If you can run fldigi with rig control then you can also perhaps run flrig. When flrig is open you can start cqrlog and put preferences/trxcontrol rig type as 4 "flrig flrig".
rigcltd should then communicate with flrig to get/set rig state.