Thank you Jan and Leo for testing and Ludo for confirming it makes sense, and of course to all bug reporters. Closing this bug. I guess I will switch e-mail programs so maybe the encoding of patches I send is not broken.
And thank you to Ludo for making important (though breaking) changes to Shepherd, making it more functional. Other than udev, the other uses of setenv in (gnu services …) look benign. Regards, Florian