If you start with "people have fundamental individual rights that should not be violated" and "initiation of the use of force is bad"
...then it follows that Ukrainian defence of their rights against the Russians, who initiated the use of force against them, is a good thing that should not be allowed to be extinguished simply because the Russians have the strength of numbers and strength of arms to do so.
Which leads us inexorably to "someone should help Ukraine to defend itself against Russia", and thence "
we should help Ukraine to defend itself against Russia", via the principle of 'if not me, then who?'.
So, do you think that the NATO nations, who have the capability to help Ukraine defend its rights against the Russian aggression, should intervene? If not, then what part of my reasoning from your premises do you take issue with?
If you come across a big bully robbing some weedy kid, and you have the means and the skills to defend the victim, you have a duty to do so. Seeing that scene and saying "It's not my place to get involved, but I am appalled at the robber's initiation of the use of force and shall tut very loudly as I walk away" would make you an arsehole, not a libertarian.