Slim kheli Can I transfer the data from a Tvheadend instance running in a Docker container to an instance running under LibreELEC?
In theory yes, provided the versions not too far apart.
Depending on how your tuners are detected in LibreELEC, maybe there could be some changes to their UUIDs. If that occurs, you just need assign your networks to your 'new' tuners. Otherwise it should be achievable.
In a standard TVH installation, the configuration files should be in /home/.config/hts.
In LibreELEC, TVH runs as a Kodi addon, so you need to use /storage/.kodi/userdata/addon_data/service.tvheadend.
You will almost certainly need to alter the 'Storage path' locations in your DVR profiles to point to /storage.