I wasn't able to get my Hifiberry DAC+ working on a fresh installed Libreelec 7.0.1.
I send my log file to the Hifiberry support team and they came back with the following reason:
The overlay file is missing. You need to inform the developers that they need to fix this. Looks like the developers didn't really test the Raspberry Pi release well enough. I would recommend to stick with OpenElec until Librelec is really stable.
So could you fix this as soon as possible?