Useful links:
See How your users are verifying their identity
https://help.salesforce.com/articleView?id=security_monitor_verification_methods.htm&type=5
Monitor Identity Verification History
https://help.salesforce.com/articleView?id=security_verification_history.htm
Two-Factor Authentication Dashboard
https://appexchange.salesforce.com/appxListingDetail?listingId=a0N3A00000EFmcXUAT
Disconnect Salesforce Authenticator
Disconnect a users one-time password authentication app
https://help.salesforce.com/articleView?id=sf.security_removing_two-factor_key.htm&type=5
