Here is the official government portal for the war in Ukraine, with a variety of ways to help listed:
If you’re okay with your donations being used for defensive and potentially offensive purposes, donating to Come Back Alive is one of the most impactful ways you can put your money to work. They post reports of what they do with donations as well:
https://www.comebackalive.in.ua/donate
As a techie, if you wish to donate your own time, there are communities you can join as well where you can have a significant impact. Depending where your skills are, you can help refugees and relocation organisations, for example. Personally, I’ve been learning Ukrainian for my girlfriend, and I’ve been helping and encouraging others to do so as well, including gifting language learning subscriptions — it’s another way to donate time to the country as it preserves a culture in danger and gets the Anglosphere closer to Ukraine (which will be especially useful post war)