Because the Mac remains connected to Wi-Fi but loses Internet access after waking, first check whether another device on the same Wi-Fi network still has Internet access.
If possible, also test the Mac on a different Wi-Fi network.
This helps determine whether the problem is limited to the Mac or specific to the network.
When the problem occurs, go to System Settings >> Wi-Fi >> Details and check the Mac's IP address, router, and DNS information.
If these details are missing or have changed after waking, note the change. Apple provides information about Wi-Fi connection details here.
If the IP address and router appear normal, check whether the problem is DNS-related.
For example, if a known IP address can be reached but websites cannot be opened by name, DNS resolution may be involved. Avoid changing DNS settings solely on the basis of this test; the result is primarily useful for narrowing down the problem.
Next, reproduce the sleep/wake sequence in Safe Mode, and then repeat it in a temporary user account.
If the problem occurs in both environments, a cause specific to your normal user account becomes less likely. If it occurs only in your normal account, investigate that account's settings or software.
If you use a VPN, firewall, antivirus, DNS utility, content filter, or other software that interacts with network connections, temporarily disable it and repeat the test.
Apple specifically recommends checking VPN and other security software when a Mac is connected to Wi-Fi but cannot access the Internet. Apple Wi-Fi troubleshooting.
Since you have already tried turning Wi-Fi off and on, forgetting and reconnecting to the network, renewing the DHCP lease, disabling Limit IP address tracking, and removing the specified SystemConfiguration files, I would not make further configuration-file changes at this stage.
When the problem occurs, run Wireless Diagnostics by holding Option while clicking the Wi-Fi icon and selecting Open Wireless Diagnostics.
Apple provides information about this diagnostic tool here.
If restarting the Mac immediately restores Internet access, note that result as well. It does not establish the cause, but it is useful information when reporting the problem.
Finally, install the latest available macOS 27 update if available.
If the problem continues, note whether it occurs on another Wi-Fi network, in Safe Mode, and in the temporary user account. These results will provide a useful basis for further troubleshooting or reporting the issue to Apple.
Regarding the Wi-Fi icon on the lock screen, I would not identify it as a new security feature based on the information currently available.
If it consistently indicates an inactive connection while the Mac remains connected to Wi-Fi, document that behaviour together with the loss of Internet access.
