Hey there!
I’m using external storage with my Nextcloud installation, connected via SFTP and public key authentication.
In Nextcloud I can choose RSA public key¹ (Apps -> Administration -> External storages -> Authentication), but I prefer my servers to be configured to ed25519 public keys only.
I suggested to add ed25519 support in GitHub², but @nickvergessen send me here, so here I am!
¹ External Storage authentication mechanisms — Nextcloud 13 Administration Manual 13 documentation
² Feature Request: ED25519 SSH-Keypairs · Issue #85 · nextcloud/external · GitHub