Confirm that you have the have the correct firmware for the device available, per this comment in the thread you linked (another Hauppauge user having success):
Hi @sa2000 ,
I found the problem on my side (should have seen it earlier)… Could have sworn the correct firmware file was in the kernel already for the Hauppauge devices but apparently not. I ran e.g. dmesg so many times and never saw the error:
[499707.765054] si2168 10-0064: Direct firmware load for dvb-demod-si2168-02.fw failed with error -2
[499707.765071] si2168 10-0064: Direct firmware load for dvb-demod-si2168-02.fw failed with error -2
[499707.765074] si2168 10-0064: firmware file 'dvb-…
