My ISP is not allowing 3rd party DNS setups, and appear to be blocking access to a users OWN modem settings such as changing your wifi password or SSID name- outrageous!

I have a Roku 3 box for TV and had been using Getflix DNS to watch UK TV. Unfortunately on this TV box you cannot set up a DNS or VPN on the device, so had been doing so via the router. As a temp' measure I had connected my chromebook to the TV via HDMI using Nord VPN, but having no remote for that it is a pain in the derriere to use!

I have a spare TP-Link Archer D7 modem which can go into 'bridge mode' and this has been suggested as a work around by setting this up with a new SSID, and setting up the DNS on that, then connecting the Roku via this. OK sounds easy - not!

Does anyone have any idea how to do this, and in fact if it will work? As a non-technical person, idiot proof instructions would help. At present, I cannot access my current router setup using all known TP link address such as 198.162.01 and others. Will this be an issue?

Many thanks.

zaza