Guide to restore Widevine L1

If for whatever reason you lost Widevine L1 certificate and your Widevine security level is now L3, you can restore L1 by following these steps:

• Flash or upgrade to MIUI 12.5.1.0 (Only tested on stock Global)

• Go to Settings > Password & Security > Fingerprint Unlock > Fingerprint paymets > Widevine L1 > Download certificate.

• After it gets downloaded successfully, you can check using an app such as DRM Info and L1 should now be restored.

Video Guide available here

Thanks to @fathigram for the hint and testing on his vayu and @kubersharma for also testing on his bhima.