That is news to me. Perhaps because all the so called USSR "Republics" had full membership?
Anyway, Ukraine had dozens of USSR nuclear missile launch sites before the USSR collapsed around 1990.
The U.S.S.R. consisted of 15 republics, but only the U.S.S.R., White Russia (Belarus), and Ukraine had seats. Russia (the R.S.F.S.R.) and the other 12 republics (Armenia, the three Baltic republics, etc.) did NOT have their own seats.
Regards,
Seems like a lot of historical facts are “new to you”.
Have you read any history books?
The USSR and Bialorus and Ukraine had individual seats in the United nations.
The thing is that the east slavic entities have had divergent histories since 1260 to the mid 1700s.