Kinda funny how things have progressed...

I work with the Smoothieware project. The V1 Smoothieboard was one of the first with ethernet onboard (although kinda borked). First thing that was advised to everyone was "never connect this to anything outside your local network"

Nowadays...it seems that warning has been lost. Even in the face of firmware updates that caused physical damage.

Something to be said for building your own printer.

I bought a bambu p1s recently and it can be used entirely offline.

You can import models to orcaslicer (open source), do your slicing, and export the g code file to SD card.

If you want to skip the SD card, block the printer's mac/ip address at the firewall and set up WiFi. Then send the print directly from orcaslicer.

That being said, my gut says bambu is going to slowly require a persistent connection to the cloud at some point. Maybe they think they are an EV car company.

Elegoo printers can be offline - you can run everything from the machine itself, as long as you have your model/s on a thumb drive. Or is that not what you mean?

Prusas are easily offline, pop an SD card or USB in and print

All of my printers are offline?

Trivial to firewall them from the internet.