The PlatformIO micro:bit board needs to be updated to reflect that J-Link is a via an optional J-Link/OB firmware update, Hardware.
The NXP KL27Z interfaces directly to the micro:bit’s nRF52833 SWD & UART for communication and programming. SWD pins are not directly available to the user.
Segger offer a firmware to flash the KL27Z with J-link/OB, so that the micro:bit can work with their Ozone debugger and IDE.
After the firmware upgrade, PIO upload_protocol = jlink and debug_tool = jlink work fine.
btw - I have a bunch of micro:bit v2 and find them very useful with multiple onboard sensors. Release candidate Zephyr 2.5.0-rc supports micro:bit v2 but, like the Arduino core, currently the LED 5x5 matrix display driver hasn’t been updated to support v2. Hopefully soon.