Hello, Dell systems seems to be very picky about the ram they accept crucial sticks are the best in my opinion.The reason you see the 2400 mhz sticks listed at crucial is because pure technical they are not incompatible they will work fine but the clockspeed on the model you have will be downclocked.If your goal is to have 16GB of ram you need to buy a kit of  2x8GB 2133 mhz as you have to use 2 sticks of the same brand .Using 2 different sticks can cause unwanted issues.
My laptop is dell inspiron 15 5567, core i5, 7th generation, 1TB HDD, 8GB RAM laptop. Will it support 2400MHz speed? Or will that 2400MHz RAM run at 2133 MHz RAM? If that's the case why spend extra money on 2400MHz RAM? According to crucial, it should support as it shows 2400 MHz RAM in compatible RAM. But I want to be sure.    This is the RAM information I get from linux:  By typing this command.
Does my laptop support 2400MHz RAM?