Just in case if anyone has missed it. Mapbox GL is a new backend (and I hope that the last one).

If you want to use it, please configure the server:

• enable Mapbox GL in profiles (select either just vector or vector and raster tiles) or, if you select Custom profile, select Mapbox GL in the Map Manager (no need to select it Settings since its a data only).
  
• update subscription info in Map Manager. For that, press "Check for updates"
  
• unsubscribe/subscribe each territory that you have.
  
• the server should indicate that you need to download new datasets. Please review and download them
  

When downloads are done, the server should be able to provide the tiles, fonts and other Mapbox GL-related data to the clients.