Don't forget kids today are very clever. They might as well as use DNS Over HTTPS (for desktop browsers) or DNS Over TLS (for android) to bypass this type of DNS filtering at router.

Confirmed, I had received the ticket number. Thanks @Kevin_Z

Bumping the topic to highlight the security vulnerability on PPPoe WAN6 IPv6: Note: Since Archer A6 is using same firmware base as Archer C6, expect the same vulnerability for C6. As I wrote before,...

Update: Support engineer responded and I am able to update to latest firmware by following the given instructions. Feel free to close the ticket. Thanks again.

Port are plugged correctly from switch to ax50 LAN. Perhaps the device is really faulty as you suspected.

@SSL_LEE Hmm, AX50 connected to a switch? Just a quick question, have you disable all the downstream DHCP servers? Might look like a broadcast storm or multiple DHCP servers issue. Try disabling DHCP...