A common frustration with WHMCS is that it only has support for one YubiKey. This module allows users to add as many YubiKeys as they need to, giving them the freedom and flexibility to verify themselves using any of their YubiKeys.
Both your staff and clients can register as many YubiKeys as they need to using this module. YubiKeys are favoured by users because they eliminate the need to type in 2FA (two factor authentication) codes from their mobile phone into their computer.
Most users have more than one YubiKey: their primary work station, one in a laptop and one on their keys. This module allows you to link as many as you like to WHMCS.