Not that long before the current Russia / Ukraine crisis, there was lots of news; especially on BBC, about human rights protests in Belarus. Belarus's dictator is friendly with Russia's Putin, but people were rising up for weeks. Then it seems like that uprising was crushed and has dropped out of the news.
A similar uprising was put down in Kazakhstan. Both former Soviet Republics. It's said that Putin fears encroachment of the west and restive populations in areas that were given up by the Russians when the Soviet Union dissolved.
What can we do about this? I don't know.
It seems like sending US troops to eastern NATO countries doesn't really help Ukraine since they say they will not enter Ukraine. They are just there to protect former eastern block countries that are now part of NATO; like Poland. They are there to protect the former Soviet Republics that, unlike Ukraine, are in NATO as well; Lithuania, Latvia and Estonia.
I doubt Russia would be a threat to those places, at least in the short run. If Russia does invade Ukraine, it will have a lot on the plate. A lot to digest so I doubt it would turn to other places; such as Estonia, for quite some time. Troops may not be the best answer as troops tend to respond to short term things.
As for arming Ukraine, itself, that might be an okay strategy, but it did kind of backfire on the US, over the long run; in Afghanistan.
When we backed Afghanistan's militias, after the Soviets invaded Afghanistan in 1979, it was said to push the Soviets out, but later some of those militias turned against us contributing to the 911 attacks.
Economic sanctions are discussed as well, but could be hard to make stick with Europe still quite dependent on oil and natural gas from Russia.
Meanwhile both US and Russian scientists are still cooperating on the International Space Station and in various other research projects including vessels at sea. I note that scientists often cooperate when politicians can't.
I don't have a clear answer, but these are things to think about.