It's now possible to donate to the non-profit GrapheneOS Foundation via bank transfers in the EU/SEPA, UK, US, Australia, New Zealand, Canada, Hungary, Singapore and Turkey. International wire transfers from elsewhere are not currently a supported option.
Discussion
This donation method mostly has no fees on our end. The only exception is a 4.14 USD fee for SWIFT wire transfers within the US as opposed to ACH payments which are free to receive. ACH is usually free/cheap on sender side so use ACH rather than sending a domestic wire transfer.
You should add the possibility to pay with Lightning. You can just publish LN Address.