Yes you can donate using Bitcoin. Just find the right agency that accepts it.
I am not sure if this is a legitimate one, but you can check it out.
https://standwithukraine.com.ua/donation/cryptoI think that's the best part on having Bitcoin although there are still very few retail shops that accepts it. Donation is not a problem though. Bitcoin is global. It has no boundaries unless they ban it in their country. But for those who needs help, I don't think they not accept Bitcoin.
This is the dilemma of online donation. Everyone should check the validity of the site as well as the authenticity that the site will indeed give such donations to the claimed beneficiaries. If not, you can always send it to known legit organizations like UN for your contribution to the cause.
As there are so many scammers today, would be hard to determine if such platform is doing what they claimed to be.