Chrome 96 - How to tell if a website is using an EV SSL certificate?

EV certificates have a specific policy OID in their "Certificate Policies" extension.

These policy OIDs vary by CA (e.g. for Entrust it's 2.16.840.1.114028.10.1.2, meanwhile for DigiCert it's 2.16.840.1.114412.2.1) as they reference policy documents published by each issuing CA. There is a common "CA/B Forum EV Guidelines" policy OID 2.23.140.1.1 which may be used alongside or in addition to CA-specific policies, but it's not actually guaranteed to be present.

As CAs must be pre-approved to issue EV certificates, browsers recognize them by having a list of specific CAs and their respective policy OIDs; for example, here's the Firefox list.

Your website's certificate has both the 2.16.840.1.114028.10.1.2 (Entrust) and 2.23.140.1.1 (CA/B Forum) EV policy OIDs, and its issuer is at least in Mozilla's EV-approved CA list, making it an EV certificate.

(As an additional hint, an EV certificate's "Subject" field will typically include very detailed information about the subject, such as the serialNumber= and businessCategory= fields. This doesn't automatically indicate it's an EV certificate, but is rarely if ever seen for non-EV certs.)