How do I use a DNS-over-HTTPS as the default DNS server system-wide (not on per-connection basis)?

I don’t see a setting in KDE that would allow me to change the DNS system-wide, I can only change DNS addresses for each Wi-Fi connection separately, but I need to change it system-wide so that on connection to a new Wi-Fi (or Ethernet) it would not connect to my IPS’s plain DNS servers.

Pi-Hole: DNS sinkhole

“Once the installer has been run, you will need to configure your router to have DHCP clients use Pi-hole as their DNS server which ensures all devices connected to your network will have content blocked without any further intervention. If your router does not support setting the DNS server, you can use Pi-hole’s built-in DHCP server; just be sure to disable DHCP on your router first (if it has that feature available).”

Fedora is supported, but my modem-router doesn’t allow me to disable for fist the default DHCP. Much depends on the modem-router that you have.