Areas missing from DVB-T/T2 setup

I recently brought a Hauppauge WinTV-dualHD to use with Plex and I’m running into an issue with the channel scan. In the dropdown for frequency selection, which I assume is based on which transmitter you use, my local transmitter isn’t listed (Heathfield). Because of this I selected Full Frequency Range which seems to pick up all the channels I expected except all the HD Freeview channels are missing after searching but they aren’t if I use the Hauppauge software that came with the tuner so there’s no issue with the tuner.
I think the channels are missing due to Plex not searching on the frequency the channels are broadcast on so is there any way to manually scan for channels or will more regions be added to the dropdown?

I too am having this issue.

I have all channels bar the HD channels.

I now have HD working for linux. The latest version from here https://github.com/b-rad-NDi/Ubuntu-media-tree-kernel-builder
I am using the 4.10 flavour. I have both tuners working, and HD recordings. DVB-T2 works
Many thanks to https://github.com/b-rad-NDi