Wondering the same. Can someone clarify? Or does it work the same for the Mi 9T like it does for the Mi 9?
Dont forget to download certificate - Ensure you have connected to the Internet;
- Ensure at least one fingerprint enrolled;
- Go to Settings -> Lock screen & password -> Manage fingerprints -> Fingerprint payments -> Widevine (L1) - Click "Certificate" button to download widevine certification key
I own a Mi 9T (International version of Redmi K20, which have a Global ROM) and when I was on stock ROM, Widevine L1 was available without any trouble. But I've switched today to xiaomi.eu and L1 disappeared in favour of L3.
So I think Widevine is included on Mi 9T and therefore not on K20, so that's why we couldn't find any certificates in the right section (because xeu rom is based under K20).