ghc-utf8-string from openSUSE:Backports:SLE-15-SP1 project
Select Your Operating System
Add repository and install manually
For standard run the following as root:
zypper addrepo https://download.opensuse.org/repositories/openSUSE:Backports:SLE-15-SP1/standard/openSUSE:Backports:SLE-15-SP1.repo zypper refresh zypper install ghc-utf8-string