EAP is supported. That’s what the username and password fields are for. The PEM/DER requirement is for server authentication. The VPN provider should provide the certificate file. For example, you can search for “protonvpn ikev2 certificate” to get the DER file for ProtonVPN. Other VPNs may use a trusted CA to sign their server certificate. You’ll need to find out what it is and upload that.