How do I add custom DVBT/T2 tunings?

Yes, a Hauppauge WinTV Dual HD. I believe I’ve got it working fine driver wise as NextPVR is showing all the channels.

Sadly I’ve seen on the reddit r/Plex channel that there are others with this issue, so perhaps it shouldn’t be marked as a supported tuner.

Really annoying as this is the final thing I want to get working in order to switch off my Mediaportal TVServer VM!