Add touch /storage/.update/.nocompat to the update process (before reboot). Your old kernel is not able to mount recent squashfs images.
Thanks for the log, it helps to avoid the error in the future.
To erase the system disk press <Alt>-<F3> at the installer screen to switch to the debug console and type
Then <Alt>-<F1> and continue to install.
Edit: in the meantime the current release is LibreELEC-Generic.x86_64-10.0.4.tar