OpenSuSE 42.3 の場合は、 root で下記のコマンドを実行してください:
zypper addrepo https://download.opensuse.org/repositories/home:ighvh:devel-kernels/OpenSuSE 42.3/home:ighvh:devel-kernels.repo
zypper refresh
zypper install ethercat
15.5 の場合は、 root で下記のコマンドを実行してください:
zypper addrepo https://download.opensuse.org/repositories/home:ighvh:devel-kernels/15.5/home:ighvh:devel-kernels.repo
zypper refresh
zypper install ethercat
15.4 の場合は、 root で下記のコマンドを実行してください:
zypper addrepo https://download.opensuse.org/repositories/home:ighvh:devel-kernels/15.4/home:ighvh:devel-kernels.repo
zypper refresh
zypper install ethercat