Be welcome!
try another tvheadend.
Perhaps the latest one will work, it will solve your problem.
Tvheadend nightly builds for LibreELEC
in your case raspberry pi 4
RPi4-service.tvheadend42-4.3-1885.zip
in the browser use: ip_raspberry_4:9981
Tvheadend is in the repository, LibreELEC, Services. (More needs to be installed).
Maybe it helps you!
step by step.
1. Install TVheadend add-ons
From main Kodi menu:
Add-ons - Install from repository - LibreELEC Add-ons - Services - Tvheadend Server 4.2 - Install
Then:
Add-ons - Install from repository - LibreELEC Add-ons - PVR clients - Tvheadend HTSP Client - Install
No configuration on the LibreELEC box is required.
2. Configure TVheadend from a PC/Mac
Find the IP address of your LibreELEC box. From main Kodi menu:
Settings - System information
On a PC/Mac using a web browser visit IP:9981 (for example, 192.168.0.1:9981)
The first screen allows you to select interface and EPG language.
Select relevant languages and select Save & Next.