Also Ed25519 can't do DH so it can't be used for encryption, whereas secp256k1 does signature and DH.
Isn't that ill-concieved DM scheme relying on secp256k1 DH.
There are ways to convert an Ed25519 key into an X25519 key for DH, libsodium has something there, but just saying.
You can use the x-coordinate on the 25519 curve and do X25519 with your Ed25519 public keys, using the algorithm "always chose the positive x coordinate". Signal does this. In fact in secp256k1 we have the same situation.
Is that what this does?
https://libsodium.gitbook.io/doc/advanced/ed25519-curve25519
