How about 1Password keyboard for iOS?

@dankinsoid

At this time the benefits are outweighed by the effort of developing a custom keyboard, when a custom keyboard could not be used to fill the primary thing 1Password is concerned with (passwords). I'm sorry I don't have more encouraging news. :( You might consider using drag & drop for instances where you want to fill data from 1Password, but neither iOS's Password AutoFill or 1Password's Safari Web Extension are available. If you're using iOS 15, and haven't enabled the Safari Web Extension yet, I'd highly encourage you to give that a try:

Get to know 1Password for Safari on your iPhone or iPad

The Safari Web Extension can fill all of the same items on iOS that it can on our desktop platforms (Logins, Credit Cards, and Identities). We don't currently support filling of passport data on any platform, but that's certainly something we can look into. 👀

Ben