We love Squarespace and recommend it to a number of our clients. The only thing we don’t like is their Google Tag Manager installation. It is a bit tricky, but you can get it done in a few minutes.
In your Squarespace backend go to Advanced, then click on Code Injection.
Now go to Google Tag Manager and grab the code
And then paste the header section into the header section and the footer section into the footer section.
Don’t forget to save it, and you’re done.