I’ve got some standing orders of 1 or 2 euros every month for bigger projects like grapheneos and kde. And for small apps that I actively use, I try to donate 5 or 10 euros now and then. It’s not much but I believe if everyone is doing their part we succeed in the long run
I donate to Signal. I intend to increase my contributions to other open source (Linux) projects this year though. I expect them to need it more than ever soon.