pfSense

Currently there is no support for certificates using X25519 and X448 public keys. Importing certificates with such keys from an external source doesn't always work either (e.g. such certs will not be listed for use by OpenSSL)

These algorithms are treated a bit differently than others in OpenSSL, since in some ways they get treated like EC but in others they do not. The algorithms are listed in openssl list -public-key-algorithms and openssl list -public-key-methods, but they aren't listed in any of the PHP OpenSSL functions or docs I've seen. For example they are not listed among the allowed key cipher constants or key types.