📚 How to donate to specific open source projects

I would like to donate to support the development of a few specific open-source projects. However, I can't seem to find a standard way to donate on a per-project basis. For example, freedesktop.org hosts the development of free and open source software, and they have a donations page/method. However, upon looking at the software they support, I find both Wayland and systemd. The thing is, while I love and support Wayland, the last thing I want to do is financially support systemd or its developers, such as Lennart Poettering.

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Is there a standard way of financially supporting open source software on a per project basis? What is the best way to donate to support the development of specific projects? Is getting in touch with the developers directly the best option?