This plugin places the GTM container code snippets onto your wordpress website so that you do not need to add this manually.
https://wordpress.org/plugins/duracelltomi-google-tag-manager/
Widgets · WordPress Plugins
Get access to data on 280,744 websites that are DuracellTomi Google Tag Manager for WordPress Customers. We know of 209,769 live websites using DuracellTomi Google Tag Manager for WordPress and an additional 70,975 sites that used DuracellTomi Google Tag Manager for WordPress historically and 93,744 websites in the United States.
Get a list of 280,744 websites using DuracellTomi Google Tag Manager for WordPress which includes location information, hosting data, contact details, 209,769 currently live websites and an additional 218,550 domains that redirect to sites in this list. 70,975 sites that used this technology previously and 93,744 websites in the United States currently using DuracellTomi Google Tag Manager for WordPress.