Implementing TCF 2.2 if site uses Google Tag Manager rather than gtag.js

Question

I need to implement Google Transparency Consent Framework (TCF 2.2) on a website that uses Google Tag Manager rather than gtag(). The Google instructions for implementing the code state the window property (['gtag_enable_tcf_support']=true) must be set before any calls to gtag () are made. Where do I put the code if there is no gtag() code on the page? Do I put it before the Google Tag Manager code, will that work, too?