Here is how Royal Decree 159/2021 applies in practice to drivers.
NOW: You must equip your car with an emergency triangle. The use of approved V16 beacons is not mandatory, although it is recommended. If you don’t have one, you can buy one, but make sure it is approved.
1 JULY 2021: Current V16 beacons become legal replacements for emergency triangles.
1 JANUARY 2026: Current triangles and V16 devices are no longer valid and connected V16 light beacons (2nd generation) will be mandatory.