The answer depends on whether external chain lubrication is beneficial for a chain with internal grease sealed with o-rings and perhaps how often you clean your chain.
One school-of-thought believes that no additional lubrication is needed. The other believes that the sprocket and chain surfaces that do not have permanent grease also need to be lubricated.
The chain manufacturers tell us that also lubricating the chain and sprocket surfaces will extend the life of these components. But a chain lube will sling-off unless designed to stick to the chain so it needs to stay tacky. Consequently it will also attract grit and road debris that, in turn, will accelerate wear faster than if you just have a clean unlubricated chain. Chain lube will also reduce power losses due to friction and shed water that leads to rust (and wear). If you live in a wet climate, you should probably use chain lube to prevent rust.
A chain newly-cleaned with WD-40 will have a coat of light oil that will effectively displace water and reduce surface corrosion of the links. It's a low viscosity oil so any excess will sling off easily, but will attract very little grit - much less that any chain lube - and it will have the same rolling friction as a number of chain lubes on the market.
WD-40, used as a one-step cleaner and lubricant is sufficient. Because it is a light oil, some fling-off will occur, so any excess should be wiped-off. USED REGULARLY, it provides good corrosion protection, low (but not the lowest) rolling resistance, and attracts less road grit than waxy chain lubes. So your chain stays very clean.
If you aren't inclined to clean and lube your chain regularly, or often ride in wet conditions that promote corrosion, there are chain lubes on the market that are designed to stick to your chain to resist fling-off and provide longer-lasting corrosion protection. Some remain tacky and attract grit, some stay slippery to the touch. All of them need to cleaned off and renewed at some point.
If you’ve decided to use chain lube after cleaning your chain, then it’s best to use straight kerosene as your cleaner because the light oil that WD-40 contains will make it difficult for the chain lube to stay attached without flinging-off.,,,