Update August 12, 2024: Bambu Lab created a page on their wiki describing the steps to update the X1/X1C printers using an SD card: https://wiki.bambulab.com/en/x1/manual/X1-firmware-update-from-SD-card
In a post on Reddit, Bambu Lab announced that the latest firmware update (01.01.02.00) for the X1E will allow its users to update it offline using a Micro SD card.
It makes sense for Bambu Lab to offer this functionality first on the X1E. As a reminder, the X1E targets professionals who might not want to risk seeing their prototype leak onto the internet and, therefore, prefer to keep the printer completely offline.
Bambu Lab said they are already working on implementing the same feature for the X1C. In the following months, they will focus on the A1 and P1 series.