How do I turn off Microsoft Authenticator?

I can't find any such security tab as Mario mentioned.

I've disabled it several times - but the next time I login I get forced to "Improve your sign-ins". I really wish Microsoft would quit trying to force their crappy products down my throat. I value my choice. I don't want Edge, Cortana, Bing or their stupid authenticator app.

You have to go to Multi-Factor Authentication in Users menu. Then Click "Service Settings". It doesn't look like a link because Microsoft is stupid and doesn't know how to make it look like a link. Then you'll see the settings you want to disable. Keep in mind, this might take 30 minutes or so for Mircosoft to replicate across all of it's servers. Pictures below

We have the same issue now and it's really frustrating, since I can not simply and DO NOT WANT to install an app on my phone. I had MFA active via SMS and exactly this happens now to us aswell. I would turn off MFA but simply can't because 1) I need to install an app, that I am not willing/easily able to install. 2) it would leave my account less secure, which I would need to get approved - and that won't happen (and would be wrong).

That seems to be the case:

https://learn.microsoft.com/en-us/azure/active-directory/fundamentals/security-defaults?WT.mc_id=Portal-Microsoft_AAD_IAM

Enforced security policies Require all users to register for Azure AD Multifactor Authentication All users have 14 days to register using the Microsoft Authenticator app or any app supporting OATH TOTP. After the 14 days have passed, the user can't sign in until registration is completed. A user's 14-day period begins after their first successful interactive sign-in after enabling security defaults.