This part gives me hope, but I have not been able to find the certificate:

Option B: cloud mode without Developer Mode

Starting with v2.0.0 the plugin can also drive a cloud-paired printer with verification left ON — no Developer Mode. This keeps the cloud features (cloud print dispatch, print history, MakerWorld) but is meant for advanced users, because it requires private slicer credentials that this project does not distribute.

Two things are needed:

1. Bambu's slicer credentials, which you provide yourself. Put slicer_cert.pem, slicer_key.pem and slicer_crl.pem in the plugin's config directory (or point at them with slicer_cert_pem / slicer_key_pem / slicer_crl_pem in obn.conf). The plugin uses the key to sign MQTT print commands and to install its app certificate on the printer. These are private credentials. This project does not ship them and gives no instructions on obtaining them — you have to find or extract them yourself, and you alone are responsible for ensuring your use complies with the applicable terms and law.

2. Two settings in obn.conf. Set block_cloud = 0 (the default 1 blocks cloud printing outright) and client_name = BambuStudio (the honest default client name is rejected by the cloud print API with HTTP 403).

With that in place you get signed MQTT commands, on-printer app-certificate install, cloud print dispatch, print history and MakerWorld — without touching Developer Mode.

What the default cloud_print = cloud_only actually uploads. Even in this mode the model itself normally stays on your network: for a print with a cloud record the plugin sends the .3mf straight to the printer over LAN FTPS, and only the record goes to Bambu — a project entry, a task entry (mode=lan_file) and a small config .3mf that print history uses for its thumbnails. That record is exactly what buys you the cloud extras: print history in Studio and Handy, and the ability to rate models on MakerWorld. The full model is uploaded to Bambu's servers only when Studio dispatches a pure cloud print (start_print), e.g. for a printer that is not reachable on your LAN.

You can limit even that: set cloud_print = try_lan_first or lan_only to print over the LAN without writing a cloud record at all, and cloud_hide_history = 1 to hide the cloud print history in Studio.

If you run neither Developer Mode nor valid credentials, the printer rejects every print / project_file command and shows on its screen:

MQTT Command verification failed err_code: 84033543