Snapmaker U1 has all their firmware on GitHub and works offline in Lan mode.

I know the community is working on a project called OpenCentauri, an open firmware for the Elegoo Centauri Carbon (great printer and amazing value for the money, but it uses a closed variant of Klipper, who knows what it's doing in the background)

You also have the DIY Voron kits, and Sovol produces Prusa-likes and Voron-likes that usually use open firmware.

Just avoid Bambu as somebody who owns an A1 (set to LAN only mode, using a microSD card to transfer print files), as aside from the lock down shenanigans and attempting to take down forks of their Bambu Slicer software (which itself is a fork of a fork), they also use a closed firmware and are heavily promoting their cloud services. I also heard that Creality is one to be cautious of too.

I am moving to Piefed at scallisto@retrofed.com (https://retrofed.com/u/scallisto)

We already have that it is called respects your freedom.

https://ryf.fsf.org/

I'm using Anycubic Kobra S1. By default its probably not the most open printer but you can install Rinkhalis to make it work with Orca slicer.

Its been in LAN mode since day one, haven't seen any outbound requests from it.

Prusa printers are totally usable offline. With Prusa Link you can benefit from some simple comfort features while remaining totally inside your local network. You can block Internet access to the printer from your router and Prusa Link will still work totally fine in you local network.

I have to check my pihole logs to confirm for sure there isn't any telemetry by default.

Agreed. We need more than scattered small brands though. Either a company forms to build anti-surveillance or aggregate all the small ones into a carefully curated marketplace.

While I don’t think prusa will go down this route the only way to ensure this is the case is a diy printer running open firmware like a voron, or using an older printer from before “cloud” was a thing for printers.

All it takes is prusa getting sold, guarantee whoever buys it will go down the route of telemetry bc it’s big money. Again, I don’t think that will happen (at least anytime soon) but the only way to guarantee it doesn’t is to control the hardware and firmware

I print by transferring gcode on a USB stick to my Prusa printer. They could be capturing all the telemetry in the world, but it's not connected to a network.