Hi Christina,
I don't use Deezer myself but from a quick search in their Help pages, it seems they don't support MFA/2FA authentication directly, if you chose to create an account using an e-mail address. They would need to introduce such support in order for you to activate MFA for your account with the Authenticator app. This has been a long-awaited feature requested by their users but even after 4 years, they haven't delivered.
However, they do support signing in using social media accounts like Facebook, Google, or Apple Id. Those providers have their own implementations of MFA/2FA. I have enabled 2FA for Facebook and Google with Authenticator and it works great.
To summarize: I don't believe you can add Deezer directly, but you could associate your Deezer account with e.g., Facebook, and if you enable 2FA for your social accounts with Authenticator, you could protect your Deezer account in this way.
Hope it helps.