I'm in a situation where I need to use HMAC-MD5 (for a learning, non-production application) and it needs to be collision-resistant.
So my question: Is HMAC-MD5 collision-resistant if the key is unknown, ie you are only given standard oracle access to an HMAC-MD5 oracle?
Alternatively, if possible you can replace "MD5" with "any Merkle-Damgård hash function for which collisions are known" (which is a more general statement).
Note that "Is HMAC-MD5 still secure for commitment or other common uses?", while related, only talks about the situation with a known key to the adversary.