Tvheadend

Trying to get an TechnoTrend TT-connect S2-4600 running on ubuntu 16.04 lts:

without install of tvheadend with official sources dmesg said:
<6>[ 554.769827] usb 1-4.3: new high-speed USB device number 4 using xhci_hcd
<6>[ 554.870986] usb 1-4.3: New USB device found, idVendor=0b48, idProduct=3011
<6>[ 554.870993] usb 1-4.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
<6>[ 554.870997] usb 1-4.3: Product: dvb-s2
<6>[ 554.871000] usb 1-4.3: Manufacturer: geniatech
<6>[ 554.871003] usb 1-4.3: SerialNumber: 000000000232
<6>[ 554.886953] dw2102: su3000_identify_state
<6>[ 554.886957] dvb-usb: found a 'TechnoTrend TT-connect S2-4600' in warm state.
<6>[ 554.886969] dw2102: su3000_power_ctrl: 1, initialized 0
<6>[ 554.888183] dvb-usb: will pass the complete MPEG2 transport stream to the software demuxer.
<6>[ 554.888309] dvbdev: DVB: registering new adapter (TechnoTrend TT-connect S2-4600)
<6>[ 554.893616] dvb-usb: MAC address: bc:ea:2b:46:07:c2
<6>[ 555.222210] i2c i2c-8: Added multiplexed i2c bus 9
<6>[ 555.279283] ts2020 9-0060: Montage Technology TS2022 successfully identified
<6>[ 555.279381] usb 1-4.3: DVB: registering adapter 0 frontend 0 (Montage Technology M88DS3103)...
<6>[ 555.280417] Registered IR keymap rc-tt-1500
<6>[ 555.280503] rc rc0: TechnoTrend TT-connect S2-4600 as /devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4.3/rc/rc0
<6>[ 555.280614] input: TechnoTrend TT-connect S2-4600 as /devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4.3/rc/rc0/input9
<6>[ 555.280876] dvb-usb: schedule remote query interval to 250 msecs.
<6>[ 555.280882] dw2102: su3000_power_ctrl: 0, initialized 1
<6>[ 555.280884] dvb-usb: TechnoTrend TT-connect S2-4600 successfully initialized and connected.
<6>[ 555.280984] usbcore: registered new interface driver dw2102
<3>[ 557.575813] dvb-usb: recv bulk message failed: -110
<3>[ 557.575907] dw2102: i2c transfer failed.

after install of tvheadend dmesg reports:
<6>[ 2866.480245] dvb-usb: TechnoTrend TT-connect S2-4600 successfully deinitialized and disconnected.
<6>[41091.376695] usb 1-4.3: new high-speed USB device number 5 using xhci_hcd
<6>[41091.477640] usb 1-4.3: New USB device found, idVendor=0b48, idProduct=3011
<6>[41091.477646] usb 1-4.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
<6>[41091.477650] usb 1-4.3: Product: dvb-s2
<6>[41091.477653] usb 1-4.3: Manufacturer: geniatech
<6>[41091.477657] usb 1-4.3: SerialNumber: 000000000232
<6>[41091.478990] dw2102: su3000_identify_state
<6>[41091.478993] dvb-usb: found a 'TechnoTrend TT-connect S2-4600' in warm state.
<6>[41091.479006] dw2102: su3000_power_ctrl: 1, initialized 0
<6>[41091.479462] dvb-usb: will pass the complete MPEG2 transport stream to the software demuxer.
<6>[41091.479569] dvbdev: DVB: registering new adapter (TechnoTrend TT-connect S2-4600)
<6>[41091.483805] dvb-usb: MAC address: bc:ea:2b:46:07:c2
<3>[41092.007577] m88ds3103 8-0068: Unknown device. Chip_id=61
<3>[41092.007717] dvb-usb: no frontend was attached by 'TechnoTrend TT-connect S2-4600'
<6>[41092.008039] Registered IR keymap rc-tt-1500
<6>[41092.008126] rc rc0: TechnoTrend TT-connect S2-4600 as /devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4.3/rc/rc0
<6>[41092.008247] input: TechnoTrend TT-connect S2-4600 as /devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4.3/rc/rc0/input10
<6>[41092.008565] dvb-usb: schedule remote query interval to 250 msecs.
<6>[41092.008571] dw2102: su3000_power_ctrl: 0, initialized 1
<6>[41092.008573] dvb-usb: TechnoTrend TT-connect S2-4600 successfully initialized and connected.
<3>[41094.298032] dvb-usb: recv bulk message failed: -110
<3>[41094.298125] dw2102: i2c transfer failed.

tvheadend does not identify the S2-4600. What does tvheadend for it to change to "Unknown device"?

Tests with a clean install of ubuntu 18.04 (without tvheadend) showed the "Unknown device"-error without firmware file, but with the firmware from http://palosaari.fi/linux/v4l-dvb/firmware/M88DS3103/ "Montage Technology TS2022 successfully identified".

Any ideas?