@Fabien31 

Hi,

If you want to know for sure, then just test it by yourself.

I can only tell you that it is not possible with the model RE305 V4. 
I've tried a few things, but no matter what I did the RE305 would always activate both, 2.4 GHz and 5 GHz, when EasyMesh was enabled.

  @woozle 

hello,

I did the test and it is impossible to choose a band on the repeater. both are automatically enabled without being able to disable one.

  @Fabien31 

Thanks for testing. So, it's very likely that all TP-Link range extenders behave the same way.

Perhaps TP-Link should consider adding this "feature" in the future.