since package Radius server does not have any dedicated forum I'm posting this here, because it may be related to Synology Directory Server, too.
I'm running some Ubiquiti/Unifi access points that are authenticating against Radius server on Synology NAS. Radius server itself authenticates...
Go to your account in Password and security:
Click on a button Change here:
After typing your account password click button Enable here:
Follow other steps and you will enable two-step verification for your forum account.