I previously had my home network hardwired with my Deco mesh in Access Point mode behind a wired router.  My home office is hard wired ethernet is also off the router and not on the Deco wifi.  After converting most of the mesh to backhaul I no longer need the hard wired router behind the modem.

Old Config:  Modem --> Router --> Main Deco M5 (AP Mode) --> Slave Decos (WiFi)

                                                  |--> Ethernet @ Desk

New Config: Modem --> Router --> Main Deco M5 (AP Mode) --> Slave Deco1 (Backhaul) --> Switch --> Slave Deco2 (Backhaul)

                                                                                                                                                                 |--> Ethernet @ Desk

                                                                                                   --> Slave Deco 3 (WiFi)

New Config Desired: Modem --> Main Deco M5 (Router Mode) --> Slave Deco1 (Backhaul) --> Switch --> Slave Deco2 (Backhaul)

                                                                                                                                                  |--> Ethernet @ Desk 

                                                                                                     --> Slave Deco 3 (WiFi)

When I attempt to switch the mode back to the default router mode, it stays in access point mode.  When opening the app, the radio button defaults to Router even when in AP mode.  However, it doesn't allow to save that option if already in AP mode.  The web-based interface does not have mode options.