Plume is present on Liberapay. All you have to do to make us a donation, is to register on Liberapay and to configure a payment method, and then to click the “Donate” button on our page. Then just follow the instructions.
It is not clear how Liberapay works since the incident they had in July 2018. However, you can be sure that any amount you give to Plume will be received by the contributors.