@David-TP Email sent. My Internet Service Provider is Chunghwa Telecom/HiNet (AS3462), and I connect via PPPoE/GPON. However, I believe that this detail is irrelevant since I have manually configured...

@David-TP Yes, both DNS servers were configured in the Internet Connection settings under DNS Address.

I was setting up NextDNS on my Deco router, which required me to enter the NextDNS IP address manually. When I set the DNS address to auto, both the primary and secondary addresses were passed down...