Almost all of the 2FA apps are just using bog standard TOTP, and have a way of getting to the cleartext OATH seed that's needed to automate it. It's typically just a few lines of Powershell, Perl, Python, etc, to take the seed, interval, and current time to spit out the right code.

Pretty much, if they offer a phone app, you can replicate the 2FA codes yourself.

Edit: Of course, protect the seed with gpg or similar if you do this.