Visit Can You Block It on same network on a non-Android device. Determine if ads are being blocked.
Check if Private DNS is enabled. To turn it off: Settings > Network & internet > Private DNS. Set to off.
Check if "Randomized MAC" (in WiFi settings) is enabled. Settings app > Network & Internet > Wi-Fi > Gear icon associated with the wireless connection > Advanced > Privacy. Switch to "Use device MAC address".