How do I annotate my HTML form fields so 1Password autofills SSH public key properly?

I can see the 1Password mini-button suggesting SSH public key autocompletion, along with the selection of available keys, but when I select a key, nothing happens. The same works perfectly on other sites (github, bitbucket).

Tried in Firefox and Edge, same behavior.

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1Password Version: 8.9.0
Extension Version: 2.5.0
OS Version: Windows 10
Browser:_ Firefox, Edge
Referrer: forum-search:https://1password.community/search?Search=public%20key%20autofill