Para 15.5 corra o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:drhax9908:branches:home:ecsos/15.5/home:drhax9908:branches:home:ecsos.repo
zypper refresh
zypper install efibootmgr
Para 15.4 corra o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:drhax9908:branches:home:ecsos/15.4/home:drhax9908:branches:home:ecsos.repo
zypper refresh
zypper install efibootmgr
Para 15.3 corra o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:drhax9908:branches:home:ecsos/15.3/home:drhax9908:branches:home:ecsos.repo
zypper refresh
zypper install efibootmgr