I am working to implement download of alternate chains in acme-tiny. At the moment I am working at the staging area. The first download from
returns a chain of three certificates. The ordered, and two intermediate ("Artificial Apricot R3", "Pretend Pear X1"). In the headers there is a single alternate link header pointing to
(with exactly the same string). Requesting this returns only the ordered certificate and the first intermediate. There is no "Pretend Pear X1" in the returned chain. As far as I understand these two requests should return exactly the same data.
Neither request returns the "Doctored Durian Root CA X3".
BTW It would be nice to have more than one chain available at staging to develop software capable of choosing between available chains.