Others have had luck by resetting their WiFi connections:
Reset network settings
To reset your network settings, tap Settings > General, then scroll down and tap Reset > Reset Network Settings.
When the device restarts, try to locate and join the Wi-Fi network again.
Note: This will clear your current Wi-Fi network settings, including saved networks, Wi-Fi passwords, and VPN settings.
Once done re-join your WiFi connection and see if your speed is better.
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