I have a similar problem. The hifiberry is not listed at all in libreelec 8.2.0.1. There was an ALSA device listed but once I remove "dtparam=audio=on" that's gone too. Running aplay -l shows the hifiberry connected with and without "dtparam=audio=on", but when it is enabled the ALSA device is BCM2835 in libreelec even when the default is the hifiberry.
debug log doesn't seem to point out anything obvious but I can post it if anybody can help?