I literally JUST set this up for myself on Openwrt (Running on my Pi4) this past week. I tried two popular solutions that both didn't work well and/or I felt were not very intuitive to setup if I needed to re implement them in the future. I started with fresh factory images after each attempt.
The third one I found a very easy method and now am currently using Control-D DNS with free ad/tracker/malware blocking over the modern DoQ protocol. Got it running in less than 30 minutes. ControlD latency appears as fast as any free DNS I've tried (Quad9, OpenDNS for years, etc), including my own ISP, so I am lucky location-wise.
I'll send you all my notes and guidance if want. Email me at my throwaway xyzx
@
duck.com