So far what I found:

My router has an option to block internet access by MAC address, which is even better than by IP.

LAN mode works via wi-fi, so no cables or flash drives needed.

Also Orca slicer is almost the same as Bambu studio, even supports printer’s camera. Feels even snappier without an account and integration with “store” or whatever that online stuff is called.

Got more interested in trying out VPN now, so I probably could observe prints from a laptop in any location.

Not as bad as I feared, not as good as it could be.

Why downvoting? It is good for community to know this, even if content is far from cheerful. Expressing criticism in comments does more for public awareness than making the message less visible.