@amit338 I think, you don't need to configure M4 as router initially. AP mode for the first Deco and then connect another Decos... Your configuration is possible, but if you connect the first Deco between you router and other wired devices of your home, then all traffic, wired or wireless will go through your first Deco. What for? Instead, connect your first Deco to the first switch if it's possible. Then resources of the Decos will be used only for wireless traffic....

RedRoger wrote

@amit338 I think, you don't need to configure M4 as router initially. AP mode for the first Deco and then connect another Decos... Your configuration is possible, but if you connect the first Deco between you router and other wired devices of your home, then all traffic, wired or wireless will go through your first Deco. What for? Instead, connect your first Deco to the first switch if it's possible. Then resources of the Decos will be used only for wireless traffic....

@RedRoger thank you for your suggestion. Valid point. Based on your input the revised setup:

2 different internet providers with respective modem+router  --> connected to the router (for failover) -->  switch --> M4 primary (in AP mode) attached to the first switch port; 5 different ethernet hubs in the home and 2 hubs are now secondary/slave deco devices in AP mode)

Kindly point me to the steps to set up the primary device in AP mode. The deco mobile application assumes that the setup will be as the router.