When Ukrainians shell civilian targets in the Donbas, is that not internal strife?

I'm not inclined to see Russian-backed separatist movements as entirely "internal".

I'm not inclined to see American-backed separatist movements as entirely "internal" either, but Ukraine is not as homogeneous as some would have you believe.

But are the people of Sri Lanka not going to suffer immensely in a different way and thus also need our aid, assistance, and attention?

Yes, and when the famine (https://www.reuters.com/world/asia-pacific/we-are-going-die-...) hits in a few months, we should - and probably will - assist. We're just not likely to intervene with the protests going on right now.