Can't speak to tax deductible donations unfortunately.
Donations I've given have gone to a few different places. Direct to the Ukrainian government via United24, SWEOD who is a nice Swedish lad who does demining work in Ukraine including a lot of training. He has ended up giving his gear to folks he trains so I throw him a few quid when I can.
I've also sent money to serhiiiam on Reddit. S/he is well vetted and seems to do good work. They have revolut as well which makes it easy for me.
There are others too but I can't find one that I think is very deserving as the video that interviewed and linked them is gone. :(
Edit: Suchomimus (incredible youtube channel covering the war) also does fundraiser requests from what I consider well vetted folks on the ground in Ukraine. I give to those where I can too.