Authenticator

Authenticator, maintained by Bilal Elmoussaoui, generates two-factor codes on Linux. It covers the case where a login prompt asks for a rotating numeric code and you would rather read it from the machine you are already working on than pick up a phone. Accounts are enrolled in the application, which then displays the current code for each of them.

The scope is the desktop: this entry lists Linux as the only platform, with no mobile companion. That has a practical consequence worth weighing before you migrate. Codes are available where the application runs and nowhere else, so anyone who signs in from a phone or from someone else's computer will still need a second way to obtain them.

The licence is GPL-3.0-or-later, so the code can be inspected, patched and redistributed under the same or a later version of the GPL. For an application that sits between you and your accounts, being able to read and rebuild the source yourself is often the deciding factor.