Missing description of ED25519-V3 private key format in rend-spec-v3.txt
rend-spec-v3.txt does not specify the format of ED25519-V3 keys in enough detail to make an interoperable implementation. And in particular, the format is different from typical Ed25519 implementations like ed25519/ref in SUPERCOP.
In contrast, the document does specify the format of RSA1024 (v2) keys in enough detail to make an interoperable implementation.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information