Yes, ST-Link V2 supports SWD so it is usable to flash nRF52. There are several tutorials on this forum, just place ST Link to search (e.g. this and this and this). And no, it is not the same as SEGGER J-Link, SEGGER tools and DLLs won't work unless you connect it to SEGGER J-Link compatible probe with alternative FW (see more about it here). However you can use tools from ST Micro (these are also integrated with some IDEs like Keil) or some open source SW like OpenOCD.
If your STM Discovery board has a ST-LINK on-board, then it appears that you should be able to make it JLink compatible, see this page.
SEGGER offers a firmware upgrading the ST-LINK on-board on the Nucleo and Discovery Boards. This firmware makes the ST-LINK on-board compatible to J-Link OB, allowing users to take advantage of most J-Link features like the ultra fast flash download and debugging speed or the free-to-use GDBServer.
SEGGER offers a firmware upgrading the ST-LINK on-board on the Nucleo and Discovery Boards.
If your STM Discovery board has a ST-LINK on-board, then it appears that you should be able to make it JLink compatible, see this page.
SEGGER offers a firmware upgrading the ST-LINK on-board on the Nucleo and Discovery Boards. This firmware makes the ST-LINK on-board compatible to J-Link OB, allowing users to take advantage of most J-Link features like the ultra fast flash download and debugging speed or the free-to-use GDBServer.
SEGGER offers a firmware upgrading the ST-LINK on-board on the Nucleo and Discovery Boards.
