In Safari for Mac 11.0.1, navigate to https://holdmail.usps.com/holdmail/
Auto fill an identity
The content fills, but the cursor goes nuts jumping between the text fields, which makes it really hard to edit anything that needs to be adjusted.
1Password Version: 6.8.4 App Store
Extension Version: 4.6.13b2
OS Version: 10.12.6
Sync Type: 1Password.com