The Tor Project has a Bitcoin donation address here: bc1qtt04zfgjxg7lpqhk9vk8hnmnwf88ucwww5arsd

Personally I believe that a Nostr account would be a waste of time for them. Tor is really in a league of their own when it comes to censorship resistence. Nostr is more comparable to a regular VPN, in the sense that you need a single jurisdiction to allow your activity compared to onion sites, which only require a single jurisdiction to allow Tor traffic.