Plume has an account on Liberapay. All you have to do to make a donation to us, is register on Liberapay, then configure a payment method, and to click on the “Donate” button on our page. Then just follow the instructions from there.
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.