Passkey registration fails on Salesforce

When attempting to register a passkey on Salesforce (Developer Edition), registration fails.
This might be a Salesforce issue or a 1Password issue.

Conditions:
- Salesforce (Developer Edition)
- 1Password for macOS, using the 1Password extension in Brave

Flow
1. Click the Register link in Salesforce "Advanced User Details -> Security Key (U2F or WebAuthn)"

2. Click Register

3. Registration succeeds on the 1Password side, but the Salesforce side shows an unhelpful red "undefined"

4. Browser dev tools console show output below