It certainly unable to locate the required root device '/dev/mapper/rhel-root' as expected and hence, fails, so you could check out block devices and partitions available from the dracut shell. Run the command "parted /dev/sda -s p" to find out partition details (assuming root file system installed on first drive which is by default ).

Also, activate the volume group and find out logical volumes present. Run the command "lvm vgscan" and then "lvm vgchange -ay" from the dracut shell to check on this.

Run "blkid" which should ideally shows your root , swap file system corresponding block devices. Please share these command details.