Matomo Tag Manager (MTM) can be configured to ignore the Google Tag Manager (GTM) data layer. For compatibility reasons, the default behavior of MTM is to keep data layer values set by GTM. As of Matomo 5, there is an option to ignore GTM data layer values. This option is useful if you are using both MTM and GTM, and the GTM data layer values are conflicting with the ones set by MTM. If you want to keep using GTM, but don’t want MTM to use the data layer values that it sets, simply check the box in the Edit container screen. This can be found by going to Tag Manager > Manage Containers and clicking the Edit Container icon next to the container you wish to update.