There was a deletion request for that package, because it is not intended for x86 and mirrors a package in the official repos. It seems like it was deleted. I remember it getting an update not to long ago.
You can still clone the aur repo and get the PKGBUILD from there: https://aur.archlinux.org/glibc-widevine.git But be aware, that it doesn't get updates anymore.
~~It looks like
/dev/sdb2
is your efi partition. Your disk names probably got swapped. It might be worth to switch to UUIDs.lsblk -f
gives you your filesystem types and UUIDs for your partitions.~~Edit: This is incorrect.