By looking at this page on their website. But I can also just tell you the answer: No, unfortunately it’s not supported. There are quite a few reasons for this. The Galaxy S7 is old and abandoned by Samsung, meaning it doesn’t receive kernel and firmware updates anymore. Even if it ran the newest release of Android, it would still lack important patches and potentially be insecure. There’s another reason why the GrapheneOS team decided to only support modern Google Pixel phones: Hardware security. Google pixel phones are equipped with what is known as a ‘secure element’ with their Titan M chips. These are tamper-resistant and can thus safely be used to store cryptographic keys and other secrets that are e.g. used for full-device encryption.