I want to use 188.8.131.52 as primary and 184.108.40.206 as secondary DNS and also enable DNS over TLS in the router itself so as the devices connected to it use the same DNS server without having to setup manually on each device.
I am using the same settings option for DNS settings in my OptiLink ONT Router but was not aware if it works.
I had applied DNS settings to all my devices as well.
But instead of CloudFlare I am using NextDNS.
I would suggest to got for it. It has better options to manage and control usage.