Simple PVR IPTV won't keep/recognise settings

I have the exact same issue.

After a reboot my channels are not loading even though everything is setup correctly.

IF i go to the settings of the simple client, deactivating and activating the client again, all channels are shown correctly.

There is some odd saving issue with the new libreelec version.

I've also noticed, that my config.txt does not keep the reading/writing rights, even after setting it to:
mount -o remount,rw /flash

Maybe I found a solution.

The Pi4 is too fast by loading up and asks for your m3u list before an internet connection is established.

Go to settings => libreelec => network => before the start of Kodi wait for network

After that your PVR client should load up normally after a reboot.