NRF52840 development kit is BLE 5.0.
If I buy a dongle is BLE 4.0 can search my NRF52840 device and connect?
NRF52840 development kit is BLE 5.0.
If I buy a dongle is BLE 4.0 can search my NRF52840 device and connect?
That should work fine. BLE 5 is backwards compatible, and is inter-operable with a device using BLE 4.0. More information can be found here.
Best regards,
Simon