Thanks very much to all who replied to my email re authenticator apps.
An authenticator app is a small program that uses TOTP codes to enable a 2fa software token secure connection between a user and their online accounts.
This type of connection is approved by many websites and is more secure than a connection via an SMS text message to a phone.
The Authy app uses TOTP codes to establish 2fa connection between a user and their online accounts.
This Authy app was available on a Debian desktop, but is now no longer available for this platform.
I do not wish to use any password managers, such as keepassxc, as they are more complicated than needed.
I just need a simple 2fa TOTP authenticator program.
I believe that two packages in the Snap Store fulfill my requirement - authme and Smart 2FA TOTP. Unfortunately I cannot find any documentation as to exactly how these packages work.
I am hoping that someone has some information about these packages.