Computer Configuration > Administrative Templates > Google Chrome > Content settings
Both
HKLM\Software\Policies\Google\Chrome
Setting the policy lets you list the URL patterns that specify which sites can ask users to grant them access to a serial port. Leaving the policy unset means DefaultSerialGuardSetting applies for all sites, if it's set. If not, users' personal settings apply. For URL patterns which do not match the policy SerialBlockedForUrls (if there is a match), DefaultSerialGuardSetting (if set), or the users' personal settings take precedence, in that order. If URL patterns conflict with SerialBlockedForUrls they will be ignored. For detailed information on valid url patterns, please see https://cloud.google.com/docs/chrome-enterprise/policies/url-patterns. * is not an accepted value for this policy. Example value: https://www.example.com [*.]example.edu