The one more function was added for 30 years old Atari 65XE - to be the USB-keyboard for a modern computer (Linux preferred).
To make this is need only Arduino Leonardo, not a lot of wires, an USB-cable. No DC-adapter of Atari will be used for this function.
Only 34 soldering points are needed to make. Because the pitch of contacts on slots of the Atari's keyboard and on Arduino is 0.1 in (2.54 mm), the process of soldering is easy.
After soldering wires from Arduino to Atari's keyboard slot, Arduino can be placed at any cozi position under the case. The USB-cable needs to be connected to Arduino and let out from the Atari's case.
Not all keys of the retro Atari correspond to keys of a modern PC-keyboard. Some keys of Atari will be with 2 functions to make all PC's commands. It is possible to make some different layouts within the Arduino sketch. Within the layout of the Arduino sketch that's here, mainly keys of Atari correspond to PC-keys, but not all.
In addition to the USB-keyboard usage it remains possible to enable this Atari in the native mode. But, of course, not at the same time when Atari is connected via an USB to a PC like a keyboard.
See "Diary" here for details and files.