Steam Desktop Authenticator

Steam Desktop Authenticator is a simple open source program for using mobile authentication on your computer. It takes up little space, has a clear interface and is quite safe.

https://steamauthenticator.net/

How to use:

Click on Setup New Account.
Enter your Steam login details login and password.
Enter the confirmation code from the mail.
And immediately link your number, confirm.
Next, you will be asked to enter a code to encrypt the authenticator's storage. It is recommended to enter, but you can leave the field empty.
Then a window with the recovery code will appear.

Be sure to write it down somewhere in a safe place.

Then everything is according to the standard: SMS comes, enter the code and that's it. Ready to use.