Hi, I tried a lot of ways to enable telnet service without success....Searching in the community, I saw that there are others people interested of this function on the R7000 AC1900 Smart WiFi Router...
Unfortunately it doesn't work on this router.
Only a program named "enable telnet" works but you can't save the configuration on the nvram so, every time that the router reboot you must re-configure all
I know that other routers can do it throught the web page that you posted but the R7000 can't.
This is what you see: