... The license requires only that the credit "be implemented in any reasonable manner". [Also note that the _text_ of our projects, while also licensed under CC-BY-SA, is licensed in way that explicitly states that a sufficient attribution is "[t]hrough hyperlink (where possible) or URL to the page or pages that you are re-using....

If it's easy to find the correct image attribution with an image search, use on the web without explicit textual attribution is reasonably properly attributed, for values of reasonableness which involve the actual ease with which the source may be found by someone exercising a minimal amount of diligence.

Alternatively, printed use with something like "photo by Joe Smith" would be far less reasonable even though it purports to name the credited party. My only motivation here is that of the reputation of the projects.

The German legal system is fascinating to me. I wish we had 3rd party standing in the US. Then we would probably get as much sustainable and power-to-gas energy as Germany has. They are way ahead of everyone there.