BLUF

A third of Russians say the Soviet Union was fully justified to invade Czechoslovakia in 1968—this suggests that Russian propaganda is effective at changing the way today's Russians see the world.

Summary

This article by Andrew Roth in the Guardian makes the following points:
A 2018 opinion poll of Russians found:

Worth noting that in 1956 Russia invaded Hungary to keep Hungary under Soviet control. See: The Hungarian Uprising of 1956 | The Runway (govcms.gov.au)

References