It would be helpful to hear what OS people are using Kodi on. Kodi PVR add-ons have to be compiled separately for each platform with a native OS compiler, so it's not something we can release a single version of and expect that it will work everywhere. Platforms like the Xbox have even more restrictions and require a special development environment.
Is everyone using Kodi Leia 18.4?
The only thing I still have not on 18.4 is the Xbox and last I looked it was 18.3. My Odroid and RPi4 are on 18.4.
Again, I am not a developer, but I thought Kodi had to be compiled for each OS...I wasn't aware the add-ons need to be also.
I would not bother working toward anything older than 18.4. I have Kodi 18.4 running on Windows 10, Windows 7, Fire Stick 4K, a Galaxy S9 and an RPi 3.5...all using NextPVR PVR add-on. All run pretty good, with the RPi being the only occasional problem child.
In general, add-ons are written in Python, which is interpreted and platform-agnostic. However, PVR add-ons are compiled binary add-ons written using the Kodi libraries (in C++, generally), and must be compiled separately for each OS/architecture platform. (Also of note: PVR add-ons on Linux are not distributed with the main Kodi package like they are for every other OS; instead they must be installed from the Linux distribution's package repositories, or compiled from source and manually installed.)
I see that PVR addons are a world of their own in Kodi. I asked about developing an addon for Channels in the Kodi forum, and received some useful feedback. Check out https://forum.kodi.tv/showthread.php?tid=346352
I am using Kodi Leia on Xbox, Windows, and FireTV stick. I would love it if you went UWP, Linux, Android, and Mac 
A channels PVR backend to any media manager (ie. Tvheadend or mythtv) would be awesome. Whether it's Kodi, Plex or Emby. Something where we can switch to live TV, find recordings and view previously saved media all in one app is the definition of cord cutting paradise!
We're working on a simple PVR add-on for Channels DVR to see how well it works and if it is worth pursuing in the long term. A pre-alpha version is available below which has been tested on Windows and macOS. Give it a try and let us know what you think.
https://channels-kodi.s3.amazonaws.com/pvr.channelsdvr-2019.09.22.1815.zip
"add-on couldn't be loaded, unknown error occurred"
Windows 10 with Kodi 18.4
Sometimes it doesn't find the DVR on the first try. See if restarting Kodi helps.
If not, grab the "Channels DVR" messages from %APPDATA%\Kodi\kodi.log
Loaded, but live channels aren't playing. Recordings play fine.
Obviously very early so the channel numbers aren't coming from the dvr and channel logos seem to be missing, this could be really great once it is feature complete.
Channel numbers: go to settings > pvr, switch to advanced and there is an option for "use channel numbers from backend".
Forgot about that not being the default
I’m guessing my architecture (aarch64) isn’t supported in the alpha yet 
2019-09-22 16:22:29.344 T:3363353456 ERROR: ADDON: Could not locate libchannelspvr.so
2019-09-22 16:22:29.344 T:3363353456 ERROR: UpdateAddons: Failed to create add-on Channels DVR Client, status = 5
Good start live TV does not play .... recordings do. Recordings not grouped.
Do other pvr clients group recordings? How are they grouped?
By Title and Movies are grouped under a Movies Category.
So you have groups enabled in the settings for your skin and view? Not all skins group recordings by default.
Tvheadend (HTSP) client does it based upon the folder it is stored in on disk. MythTV does it by group or series rather than storage local on disk.
That is the way the KODI HDHomeRun unofficial addon does it.