The TP-Link Deco Mesh WLAN routers can be used with any other router or modem, but please note that a Deco WLAN Mesh router has its own DHCP server, i.e. in order to be able to communicate optimally with all devices in your home network, only one Deco Mesh WLAN device should be connected to the router of the Internet provider. All other LAN connections of the Internet provider would receive IP addresses from the Internet provider router. The simplest solution is to use an external Gbit switch on the Deco unit that is connected to the ISP's modem or router (this avoids the problem of the units being unreachable from each other). An 8-port Gbit router is available from Digitec for as little as CHF 33.

The mesh only works with each other, not with foreign devices. I have Salt at home and operate it independently of the router.