For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:manfred-h:server:messaging/openSUSE_Tumbleweed/home:manfred-h:server:messaging.repo
zypper refresh
zypper install telegram-desktop
For openSUSE Slowroll run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:manfred-h:server:messaging/openSUSE_Slowroll/home:manfred-h:server:messaging.repo
zypper refresh
zypper install telegram-desktop
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:manfred-h:server:messaging/15.6/home:manfred-h:server:messaging.repo
zypper refresh
zypper install telegram-desktop