Hi @Techster76
You don’t need to sign up for a Duo account to access the FINRA Reporter Portal, you just need to enroll as an end-user. Duo admin accounts are used to protect applications, and the portal you are accessing is already protected. Hope I explained that clearly 
it’s a little confusing.
I found these instructions on how to enroll from a FINRA CAT Onboarding Guide: (page 20)
New users will be prompted to complete these steps before they can access the Reporter Portal.
- Navigate to the Reporter Portal based on your connectivity method
- Click Start setup to begin the enrollment process.
- Select the type of device you will use for authentication (mobile phone, tablet, or security key) and click Continue.
- Skip to step 5 for security key
- Complete the following steps to enroll a security key in Duo MFA:
a. Click Continue to begin enrolling your security key.
b. Insert your security key into the USB port on your computer and, if needed for the model used, tap the key or press the button.
c. A message will appear confirming that your enrollment was successful.
We have a guide to using security keys with Duo which you may find useful. Check it out here: https://guide.duo.com/security-keys
And yes, Duo supports WebAuthn/Fido2 - even the free version!
I hope that helps! Thanks for using Duo and posting here in the community. 
