Where are the documents for the modules ?

I tried to flash some examples to the XBee in my mesh developers kit but it fails. The examples were written in 2017 so I guess the modules have changed

Have you looked at this?

Programming XBee modules
Firmware on the XBee and XBee-PRO ZB modules can be updated through one of two means:
:black_small_square: Serially
:black_small_square: SIF header.
Each method is described below.
Where possible, configuration settings are retained regardless of firmware changes. This can lead to difficulties,
especially when changing firmware among variants of the same release with different default configuration
settings. The best practice after changing a firmware load is to do a RE (reset to factory defaults), explicitly set
the configuration registers to desired settings, and then do a WR (write configuration settings).
Serial firmware updates
Serial firmware updates make use of the XBee custom bootloader which ships in all units. This modified
bootloader is based on Ember’s standalone bootloader, but with a modified entry mechanism. The modified
entry mechanism uses module pins 3, 9, and 16 (DIN, DTR, and RTS respectively).
The XCTU program can update firmware serially on the XBee and XBee-PRO ZB modules. Contact Digi support for
If an application requires custom firmware to update the XBee firmware serially, the following steps are required.
Invoke XBee bootloader
See XBee bootloader for steps to invoke the bootloader.
Send the firmware image
After invoking the bootloader, the Ember bootloader will send the bootloader menu characters out the UART at
115200 b/s. The application should do the following to upload a firmware image.
1 Look for the bootloader prompt BL > to ensure the bootloader is active
Module support Programming XBee modules
XBee/XBee-PRO Zigbee RF Modules User Guide 177
2 Send an ASCII 1 character to initiate a firmware update
3 After sending a 1, the EM250 waits for an XModem CRC upload of an .ebl image over the serial line at 115200 b/
s. The .ebl file must be sent to the EM250 in order.
If no serial transaction is initiated within a 60 second timeout period, the bootloader times out and returns to the
menu. If the upload is interrupted with a power cycle or reset event, the EM250 will detect an invalid application
image and enter bootloader mode. The entire ebl image should be uploaded again to recover. If an error occurs
while uploading, the EM250 bootloader returns an error code from the following table: