We do OTA service through a HTPC, (Home Theater Personal Computer). I run Windows 7 with Windows Media Center so no cost for guide service, have 2 Silicon Dust Dual tuners plugged into our router so we can record up to 4 programs at the same time. Total 1 time cost for computer, extra 3 TB hard drive and the 2 dual tuners was less than $400. That has been more than 4 years ago now. We can also stream through the computer if there is something we want to watch online.
I had a similar setup for many years... two HDHomeRun tuners and free guide data via WMC. At first we ran WMC on a Win7 PC hooked up to the TV. Later, we ran Kodi on two Fire TV boxes and used a utility called ServerWMC to feed programming, guide data, and DVR functionality to Kodi.
Once set up, it was fairly reliable, but it did have some quirks. Guide data would go absent for no apparent reason and then come back a few days later... sometime all channels, sometimes just a few. WMC would occasionally lose the channel data, which required me to re-run the setup process and channel scan. Same would happen with the tuners from time to time. Connectivity was usually good with minimal buffering but we did have one local channel that suffered from near-constant pixelation. That channel worked fine straight into the TV so it was somehow related to the whole WMC setup and I never came up with a resolution.
Anyway, that was then. This is now with PS Vue and Cloud DVR. Much simpler, less hassle, and more reliable. But at a cost. Also, I think 2018 is the year Microsoft will drop guide support for WMC.