Here's a recent announcement from MSF concerning their operations in Ukraine:

The drastic escalation of conflict in Ukraine has led Doctors Without Borders/Médecins Sans Frontières (MSF) to make the painful decision to halt our normal medical activities in the country.

Immediately before the escalation, we were in contact with several hospitals in the Donetsk and Luhansk regions to provide training in emergency medicine and surgical preparedness, and yesterday our team provided one mass casualty kit, with supplies for treating traumatic injuries, to a hospital in Mariupol. As hostilities continue, assuring people’s access to health care and medicines will be critical.

MSF teams in Belarus and Russia stand ready to provide humanitarian assistance where needed. We are looking to send teams to neighboring countries to be ready on stand-by, either for response in Ukraine or to provide humanitarian medical assistance to refugees seeking asyl     um abroad. Our supply centers are currently working on preparing medical kits for rapid dispatch.

Thank you, as always, for supporting us as we rush to respond. We’ll continue to update as our response changes.

Thanks Michel for your effort to research these charities! As so many others, I am now wondering what would be the best way to provide support to Ukraine. Of course one would like to find a reasonably effective charity and above all avoid possible scams. Your article is already helpful in providing some insight into a few of the alternatives. Of course it's not quite so simple as to say that the charity with the least amount of overhead cost is always able to provide the most benefit on-site so it's obviously important to examine them from many angles as you have done. This is not easy. Many thanks for your sincere effort!