epubcheck from Documentation:Tools project
Select Your Operating System
Add repository and install manually
For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Documentation:Tools/openSUSE_Tumbleweed/Documentation:Tools.repo zypper refresh zypper install epubcheck
Grab binary packages directly
Add repository and install manually
For SLE 12 SP5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Documentation:Tools/SLE_12_SP5/Documentation:Tools.repo zypper refresh zypper install epubcheck