For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ahmedmoselhi2:branches:system:snappy/openSUSE_Tumbleweed/home:ahmedmoselhi2:branches:system:snappy.repo
zypper refresh
zypper install snapd
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ahmedmoselhi2:branches:system:snappy/15.6/home:ahmedmoselhi2:branches:system:snappy.repo
zypper refresh
zypper install snapd
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ahmedmoselhi2:branches:system:snappy/15.5/home:ahmedmoselhi2:branches:system:snappy.repo
zypper refresh
zypper install snapd