it seems there is no such repo for this architecture (aarch64)... (no repo to install FROM Libreelec repo)
hummmm ... wait ... here is on github :
GitHub - linuxserver/libreelec-addons
I'll try when I'll be back to 7.9. I am currently on 7.0 with the docker bug.
I also have to find how to connect my containers to my network (VPN)...
Thanks for checking. Then kszaq may have to manually add it to his builds