Gfilui

When i connect my EVOLVEO SIGMA T2

and type lsusb in terminal,

linux identifies new device as ID ID 0572:c68a Conexant Systems (Rockwell), Inc.

but w_scan command returns only error

w_scan version 20170107 (compiled for DVB API 5.10)
using settings for CZECH REPUBLIC
DVB aerial
DVB-T Europe
scan type TERRESTRIAL, channellist 4
output format vlc xspf playlist
output charset 'ISO-8859-1'
Info: using DVB adapter auto detection.
main:4007: FATAL: ***** NO USEABLE TERRESTRIAL CARD FOUND. *****
Please check wether dvb driver is loaded and
verify that no dvb application (i.e. vdr) is running.

How can I install driver for EVOLVEO SIGMA T2 and then successfuly scan for dvb-t & dvb-t2 channels ?

Your device 0572:c68a is supposed to be covered by the driver dvb-usb-cxusb, however, the exact usb.id isn't included yet in the version included in the latest stable Ubuntu version, 17.10 and, therefore, earlier. Let's build a newer driver.

Please try this with a working internet connection:

sudo apt-get update
sudo apt-get install -y git build-essential
git clone https://bitbucket.org/CrazyCat/media_build.git
cd media_build
./build --git https://github.com/crazycat69/linux_media latest
sudo make install

It builds with a few possibly harmless warnings for me. The new driver reports:

$ modinfo dvb-usb-cxusb | grep C68
alias: usb:v0572pC68Ad*dc*dsc*dp*ic*isc*ip*in*
alias: usb:v0572pC689d*dc*dsc*dp*ic*isc*ip*in*
alias: usb:v0572pC688d*dc*dsc*dp*ic*isc*ip*in*

As you can see, your device is included. As a part of the install process, the needed firmware is also installed.

Reboot and tell us if there is any improvement. I will have a few more instructions.

EDIT: You have compiled the driver for your current kernel version only. When Update Manager installs a later kernel version, also known as linux-image, after the required reboot, recompile:

cd media_build
make distclean
git pull
./build
sudo make install