How to find out which BLE version is supported for a given Nordic SDK + SoftDevice.
From which version of Nordic SDK is compliant to Bluetooth 4.2 ?
The NRF52 series supports BLE 5
The specific softdevice version will depend on the exact NRF52 SoC. Examples of softdevice versions for the NRF52 series include s132 and s140.
The compatibility matrix for each NRF52 SoC model from this link might also be useful.
All our nRF5x series devices support BLE (4.2 or newer). So does all our SDKs from v.11.0 to 15.3 (most recent). If you wonder where to start out, we recommend purchasing an nRF52 Development kit with a JLINK debugger and an nRF52832 chip on board that supports BLE (4.2 and 5.0) and using SDK v.15.3 and SoftDevice S132 v.6.1.1. The links shared by thoric_fish should be helpful as well!
Keep in mind that we generally recommend the nRF52 series chips for new BLE designs, as the nRF51 series SDKs and SoftDevices are no longer updated regularly.