TVheadend service is running and can access the web interface to configure. However, the frontend client will not stay enabled so TV service does not run in Kodi.
Also - if possible, could the TVheadend addon be compiled from the latest code? The ATSC EPG grabber works on the last Milhouse version for OE 4.1-1724.
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After uninstalling and reinstalling the TVH addons - they are now staying enabled and TV is working.
As for the updated addon - totally understand if we need to wait for the official TVH 4.2 release. Maybe someone will eventually write a front end configuration program for TVH that can be used within Kodi!