The safest way to do so is to donate the funds to the NixOS OpenCollective (https://opencollective.com/nixos). The Foundation does not maintain a wallet as this would be complicated from a finacial/legal/tax perspective.
This brings up an important question, the Starknet wallet described as for the binary cache has had about $40-$50k go through it and has been cashed out. What is the status of these funds?
Looks like Mercury donated about 9k EUR to the Open Collective, thank you! S3 Cache Long Term - Open Collective