The request message was malformed :: Error creating new order :: Domain name "svn.example.com" is redundant with a wildcard domain in the same request. Remove one or the other from the certificate request.
I remember that a few months ago it was possible to apply for such a certificate.
It was, briefly. Let's Encrypt never desired to support overlapping certificates, but they enabled wildcard support before updating the CA software to block overlapping wildcards.
The SAN list is alphabetized, but the first argument is used for the CN.
I just did it with a staging certificate.
Issuer: CN=Fake LE Intermediate X1
Validity
Not Before: May 28 02:02:14 2018 GMT
Not After : Aug 26 02:02:14 2018 GMT
Subject: CN=*.letsencrypt.mattnordhoff.info
X509v3 Subject Alternative Name:
DNS:*.letsencrypt.mattnordhoff.info, DNS:letsencrypt.mattnordhoff.info
Cool ! ! !
Now if his devices are able to match the SVN request with * he is good to go.
If not, I say, feed them SVN and SNI the rest over a separate vhost config.