Since my iPad just became obsolete, could this become a security problem for me with 1Password?

Hello jazzman! 👋

1Password for iOS currently requires iOS 16.4 or later: System requirements for 1Password

I always recommend running the latest version of iOS/iPadOS so that you can take advantage of the latest feature and updates. That being said, Apple does support several versions of their operating systems concurrently. For example, they just released an update for iOS 17 last week: About the security content of iOS 17.7.2 and iPadOS 17.7.2 - Apple Support

As long as your iPad still receives security updates you'll be able to use it safely. For more authoritative advice on how to keep your iPad secure, I recommend reaching out to Apple Support.

I hope that helps. 🙂

-Dave