The UK, national smart meter effort. Sub gig, supported by three silicon providers did Zigbee sub-gig for the last mile, tough to penetrate homes and buildings. Running 3.0 on which means it will port very easily but sub-gig is much more regulated country by country than 2.4. You can search. This article covers the initiative but doesn't call out the sub-gig detail: https://telecoms.com/opinion/467631zigbee-and-the-smart-mete...