You do not need to give it internet access for LAN mode to function, but you lose a LOT of features that the cloud app and mobile app give you. For example, you can no longer do anything with the camera in LAN mode, even from the official Bambu Studio app. So no timelapses or ability to check in on it from even just elsewhere in my house.

There's also other limitations of it in features I don't really use, for example IIRC the RFID stuff they do with their print spools stops working.

I'm not sure why you would need to give it internet access. I think even the firmware updates work via SD card.

They just introduced firmware updates via SD card in the most recent released version, prior to that you had to put the printer online and associate it with an account to get firmware updates.

But yes today there is no need to use their cloud services unless you want to control the printer with their phone app. And the printer works totally fine completely isolated from the internet.

The now aborted proposed update would have required using a binary shim from bambu with an embedded 1 year lifetime SSL cert to speak the the printer at all, even when in lan mode.

Bambu Companion (unfortunately iPhone only) does more than Handy and works on LAN. Using it today in fact! https://www.youtube.com/watch?v=LZpDQN9zgUI