nRF52811 emulation on nRF52840 DK
Overview
The nrf52840dk_nrf52811 board is a modified version of the nRF52840 DK that enforces the limitations imposed by the nRF52811 IC, which is a variant of the original nRF52840. Since Nordic does not offer a development kit for the nRF52811 you can use this board to develop for this IC while using the nRF52840 Development Kit (PCA10056).
See nRF52840 DK for more information about the development board and nRF52811 website 1 for the official reference on the IC itself.