The reason, why USB 2.0 cameras are not found in Linux depend on the camera series.

DxK 22, DxK 42 and DxK 72:

These cameras needs a firmware update for becoming UVC compatible. Please refer to https://www.theimagingsource.com/documentation/tiscamera/firmware-update.html

The firmware files are in the tiscamera/data/firmware/usb2 directory. The versions with four digits are or Linux, the version with three digits are for Windows. 

There is no difference in firmware betwen DxM and DxK models. 

DxK 21,  Dxk 31 and Dxk 41

These camera models are UVC compatible, but the UDV rules must be adapted. Please refer to

https://theimagingsource.deskpro.com/de/kb/articles/using-usb-2-0-ccd-cameras-in-linux

Annotation:

x can be F, B and M for color (F = german Farbe), bayer and mono