@CVVT Does the ISP router replace something else?

The ISP router will not be "in" the mesh.  It will be used by the mesh to access Internet.

I suggest running the Deco mesh in "Access Point" mode, and let the router assign IP addresses to all devices.

  @yves_b Thanks for your support. 
 

The HX220 installed by the ISP technician is a new installation in a new house. 
 

I already purchased 3 Deco X 50 devices. 
It would be nice if the HX220 could be used to also extend the Deco mesh. 
 

kind regards

CVVT

  @CVVT 

Some models of Deco are compatible with EasyMesh, hence could make a single mesh with the HX220.

See more info in https://community.tp-link.com/en/home/forum/topic/710684.