Multiple DVRs are pretty seamless. They will talk to each other and whichever has more free space at a time will make the recording. The HDHomeRun app will show all recordings from all DVRs together.
If you don't have guide listings for your channels you should post in the Guide Issues subforum of the software forum so SD can add listings to the channel. They can't help the station actually being dark, but at least they can make it show what should be there.
ATSC 3.0 Forum