Can you please give us ssh -V, and describe the sandbox environment? Does it
affect which ssh version is used?
(I'm mildly annoyed that I have to ask again. You are not forthcoming with
information about your environment. macOS is somewhat alien for us, and if you
want help with tracking down the issue, you need to give us more information.
Note that we really do make an effort, and we have a macOS build slave that does
not see these issues:
https://jenkins.gnupg.org/job/gnupg/XTARGET=native,label=macos/
(though we get our build dependencies from pkgsrc, and you get it from your
packages I guess, so there are bound to be differences).)
From your latest log I see that the version of ssh used supports ed25519, so
this must be version newer than 6.5.
I just committed a patch that dumps the ssh version and the path to the binary
when executing the test: