Answered by the 3DPrinterOS team
3DPrinterOS connects Bambu Lab printers in LAN Only Mode, so print data does not go through Bambu Lab's cloud. Jobs travel from the 3DPrinterOS Cloud Client on your own network to each printer, and your files stay on infrastructure you choose: managed U.S. or EU cloud, your own cloud account, or air-gapped servers.
LAN Only Mode on its own keeps data local but leaves out fleet tools such as sign-in, queues, cost tracking and audit logs. 3DPrinterOS adds them:
Setup needs the printers on the same network as the client host, ports 990 and 50000-50100 open between them, and a fixed IP for each printer. Bambu Farm Manager and 3DPrinterOS cannot manage the same printer at the same time.
See Bambu Lab security and privacy and the Bambu Lab fleet management page.