Comment by wallaBBB

There are actually 2 Nordic SDKs, nRF5 (now in maintenance, but still in many supported products in the field) and nRF Connect (bundled with Zephyr). Later gives a lot of access to both Host and Controller part of the stack and for commercial products that are not simply flipping a lightbulb it is still a standard. ESPs are good for quick hacks and more competitive with Nordic if low power is not an imperative.