This is a console application which is a self hosting Web Api which mimicks an HDHomeRun. You will need to run it as administrator and modify the config file to change the values appropriately. You'll also need to allow port 5004 through your firewall. Here are the settings is HdhrWebIfInterface.exe.config
IpAddress - The Ip address of the machine you are running this application on
Port - the port used to communicate, leave at 5004 for now
WebIfIpAddress - The Ip address of your zgemma box WebIf
WebIfPort - The port of your zgemma box WebIf
WebIfStreamPort - The streaming port of your zgemma box
UseTestWebIfData - Setting this to "1" will use the test data in the folder instead of connecting to a zgemma box. This allows me to simulate the HDHomeRun without even turning on the zgemma box. Well, up until the point it needs to actually record something, then it fails.
Then just go to Plex and add a DVR in settings. Plex won't be able to automatically detect it on your network so you need to add the ip and port manually. e.g., 192.168.1.100:5004.
If this works for you and there's any demand for it I might consider updating and supporting it.
Oh, forgot to add: I'm using a WooshBuild which has the channel names with numbers included such as "101 BBC One". I use this to get a channel number and name so if your channel names are not in that format the app won't pick them up. Have a look at the test data xml file for the expected format. If it doesn't pick yours up then rename a channel or two and try again.