My app is called "The Offline App" and is able to display live TV from the HDHomeRun, live audio from nrsc-5 broadcasts, ADS-B data from planes, and a lot more, without the internet. Since fundamentally the purpose of this app is to not connect to the internet at all, it was crucial that I made the app source guide data directly from broadcast signals. This was relatively easy for the ATSC 1.0 channels as the app can quickly request the full transport stream per RF channel, parse, and display the data contained in the PSIP.
For ATSC 3.0, the guide is much better. Channel logo images and programming poster images are being sent over the broadcast signal, in addition to a much longer guide compared to ATSC 1.0 channels. The only way that I was able to get this working was to have the app request a pcap from a DEV tuner on the LAN once the app discovered the channel lineup, parse the saved pcap, extract the ALP UDP payloads, parse the LCT packets, reassemble each object, decompress if using gzip, save the images and XML, match it based on the XML, and pass it to the guide UI. This took many days of tinkering around but I was able to get it to work. This honestly is overkill for simply trying to display simple guide data. It would be nice if I could make the app work with standard 4K models so people without the DEV upgrade could receive guide data offline.
-Dylan