Thank you very much.
Do you know what kind of user I need to create? Is enough with the user that is created with the initial wizard with these rights?
BTW, I've followed this Youtube tutorial (using LE repositories) to setup the TVHeadend and there is not reference to configure user/password. Is there this configuration in any file?
Start with clean installation Burn image on SD card. Install tvheadend42 and pvr.hts from LibreELEC repository. Don't create any new user/password. You don't need it. Default user '*' with no password is enough.