Why did Nordic change the way to enter the bootloader?

[JosePastor23]

Pretty much it's the title. Why is no longer permited use the GPREGRET register to decide whether if boot in the bootloader or app?.

[Rune Holmgren]

The new Secure DFU bootloader released in SDK 12.0.0 does not yet have any production quality buttonless support. The experimental buttonless example was implemented using a flag in the DFU settings flash page to indicate that DFU mode should be entered upon reboot. This is likely to change to use GPREGRET in the production version, but the decision has not yet been made final. It might depend on implementation details such as how the bond sharing between bootloader and application is eventually implemented.

You may set your own conditions for when to stay in bootloader mode, like reading GPREGRET, by implementing a function nrf_dfu_enter_check(void). The function implementation in nrf_dfu.c is weak to facilitate such custom conditions.

[JosePastor23]

Great, thanks for the aclaration Holmgren