This describes how to turn off IPv6 on older Macs.
Turning off IPv6 can resolve some obscure networking issues. These instructions work for operating systems such as Monterey, which use "System Preferences" instead of "System Settings" used in more modern versions of the OS.
Go to the Apple menu, then choose "System Preferences". Click "Network". Click "Wifi" in the list on the left. Note: if you connect with a cable or other interface, choose it instead. Click "Advanced". Click the "TCP/IP" tab at the top. Next to "Configure IPv6", choose "Link-local only". Click "OK". If requested, click "Apply".