Bambu Lab posted today a message on Reddit inviting users to register to join a private beta testers group.
So if you have an A1 or A1 mini and are interested in testing new firmware, you can sign up using this link: https://bbl3d.cc/s/o9tyi
As a reminder, beta firmware is likely to have issues. Therefore, we do not recommend signing up for the beta group if you use your printer in production or if you rely on it for important matters.
Bambu Lab says they will select who will receive the firmware on Monday or Tuesday. They will then invite the selected participants to a private beta area on the Bambu Lab Forum so you need to be a member of the forum to participate. The beta should begin in about a week, but Bambu Lab says this can easily be postponed.