Just received a WinTV-dualHD today and encountered the same problem with a bit older build of coreelec, running on GT-King Pro. I can confirm that after rebuild from head of coreelec-9.2 branch (9f6f71fbe4) the problem reported in this thread is fixed.
However I get another problem: Hauppauge WinTV-dualHD tuner is not working in any USB 3.0 port of GT-King Pro. It works only in the one USB 2.0 port (marked as OTG) provided by GT-King Pro.
When in usb 3.0 port, following messages are logged:
[ 2476.674353@0] si2157 5-0060: downloading firmware from file 'dvb-tuner-si2157-a30-01.fw'
[ 2477.130041@1] em28xx 1-1.1:1.0: writing to i2c device at 0xc8 failed (error=-5)
[ 2477.386088@1] em28xx 1-1.1:1.0: writing to i2c device at 0xc8 failed (error=-5)
[ 2477.642023@2] em28xx 1-1.1:1.0: writing to i2c device at 0xc8 failed (error=-5)
[ 2477.642033@2] si2157 5-0060: firmware download failed -5
[ 2477.642077@2] em28xx 1-1.1:1.0: DVB: adapter 0 frontend 0 frequency 0 out of range (48000000..870000000)
[ 2477.898086@0] em28xx 1-1.1:1.0: writing to i2c device at 0xce failed (error=-5)
[ 2478.154087@0] em28xx 1-1.1:1.0: writing to i2c device at 0xce failed (error=-5)
[ 2478.410099@0] em28xx 1-1.1:1.0: writing to i2c device at 0xce failed (error=-5)
[ 2478.410232@0] em28xx 1-1.1:1.0: DVB: adapter 1 frontend 0 frequency 0 out of range (48000000..870000000)
[ 2480.938330@2] em28xx 1-1.1:1.0: writing to i2c device at 0xc8 failed (error=-5)
[ 2481.194134@0] em28xx 1-1.1:1.0: writing to i2c device at 0xc8 failed (error=-5)and it is not possible to show any tv station.
While when running in the usb 2.0 port, it is fine, no error message present and both tuners work simultaneously with tvheadend.
I guess this is probably GT-King Pro specific.
I planned to get a second WinTV-dualHD to be used with GT-King Pro, but that would need to use usb 3.0 ports as only one usb 2.0 port is available.
Any idea how to solve this?