I upgraded from v2.7.0 to v2.8.0 of the nRF Connect SDK and noticed that the UART was no longer working.
It seemed the UART receives one byte and calls exit. Transmit doesn't work at all using interrupt.
The echo_bot example worked for me and I figured out the culprit was the power management configuration.
Way to reproduce:
Create echo_bot example using v2.8.0 SDK
Add to prj.conf:
CONFIG_PM_DEVICE=y
CONFIG_PM_DEVICE_RUNTIME=y
Tested on the nRF25840-DK.
It seems only the interrupt API is affected by this. Polling and Async API work fine.