FOSS devs can do FOSS work only because of the relative luxury conditions of their imperial core countries, which comes at the expense of global south countries.

In other words, they can do that because their countries imperialist relations with the global south, this is the reason that most FOSS projects come from the US and Europe.

In some way FOSS work is a way for these people to give back to the world, i think its fine to donate to these projects regardless of their location.