Hi @max_civino ,
the Beacon API is used to send a request to an external web server. So it isn't the Tealium code of utag.link that has to support the Beacon API, but the vendor specific tag template. For example, the newer versions of the Google Analytics tag template have the configuration field "transport method", which can be set to "beacon". This will change the GA tag to use the Beacon API instead of a standard image request.
I am not sure about the adaption status of other vendors but I think it is not yet widely supported.