The Afghanistan response was to a direct attack on the United States, so it is no surprise that even the Libertarian leaning Republicans approved of it - at least at first. The original Iraq resolution had 6 Republicans who voted against it, notably Ron Paul who has always been the most visible face of the Libertarian caucus.
Ron Paul was the one that immediately came to mind for the Libertarian prototype in the mind of many conservatives.
His son, Rand Paul, is more of a mixed bag. But Ron Paul can still be pointed at to demonstrate that at least where Libertarians are concerned, non-interventionism does tend to reign supreme on their agenda. Russia hasn't attacked the US, while there are NATO implications in what they're doing in Ukraine, the Libertarians also want to dismantle NATO, or at least, pull the US out. So from their perspective, the US shouldn't be involving itself in Ukraine. Because the US has no
direct national interests in that fight.
It isn't that they're pro-Putin, they're anti-intervention, no matter who the intervention involves.
I don't view that position as particularly tenable, as that's how you allow small problems to grow into even bigger ones in due time. As happened in WW2 because the US voters wanted to be completely "hands off" on foreign affairs during the 1930's up through 1939 for most, and December 7th, 1941 for a great many.
