I’m getting a very similar issue. I had a USB tuner running fine earlier this year but stopped using plex for a while. I have just started using plex again. I have updated the server to the latest version and it won’t find my USB tuner.
This is on a 2017 16GB shield with all the latest updates that have just been released and the latest version of the PMS(Version 1.14.1.5488). Must be a software issue if the older version of PMS picked up the USB tuner OK.
Logs
Dec 21, 2018 21:23:20.770 [7881] INFO - [I] dvb_device_factory_t::get_device_list ()
Dec 21, 2018 21:23:22.781 [7881] INFO - [I] SAT2IP - discover_satip_servers(): no servers found
Dec 21, 2018 21:23:23.186 [7881] INFO - [I] v4l::DeviceGetList_impl. getting v4l device list
Dec 21, 2018 21:23:23.195 [7881] INFO - [I] onetv_factory::DeviceGetListEx >>
Dec 21, 2018 21:23:23.195 [7881] WARN - [W] onetv_factory::DeviceGetListEx. libusb_init returned an error -99
EDIT: my tuner is a Hauppauge WinTV-dualHD which is listed as supported
