Yes, it is possible to prevent cross-domain linking for a specific sub-domain in Matomo.
To do this, follow these steps:
Log in to your Matomo account and go to the website settings for the sub-domain you want to modify.
Under the “Tracking Settings” tab, click on “Cross Domain Tracking”.
Enable the “Disable cross domain tracking” option.
Add the domains that you want to block from cross-domain tracking in the “Domains to exclude” field.
Click on “Save” to apply the changes.
By following these steps, Matomo will prevent cross-domain linking for the specific sub-domain and any domains listed in the “Domains to exclude” field.