Trying to add Google Ad Conversion Tag using Matomo Tag Manager


I try to achieve to add the Google Conversion Tag (Google Ads) using Matomo Tag Manager. I am well aware that there is even a custom solution for this provided by Matthieu Abry.

But I need to wait for my admins to try this on our on prem installation of matomo.

In the meantime I tried the following:
I added the google tag and set the trigger for it to “DOM ready”.
Now when I try to fire on specific URLs I see the following error message in the console:

Uncaught ReferenceError: gtag is not defined
    at <anonymous>:2:3
    at insertNode (container_8Jipm5bo.js:55)
    at moveNodes (container_8Jipm5bo.js:56)
    at (container_8Jipm5bo.js:61)
    at h._doFire (container_8Jipm5bo.js:31)
    at (container_8Jipm5bo.js:31)
    at container_8Jipm5bo.js:29
    at Object.setUp (container_8Jipm5bo.js:62)
    at f.setUp (container_8Jipm5bo.js:28)
    at (container_8Jipm5bo.js:34)

So I assume that the tag is inserted to late into the page. How can I make sure that the google tag is already loaded before the trigger try to fire it?

I even set the google tag to “HEAD START” and all other tags to “Head end”.