Wi-Fi connectivity issue on my Apple devices

If all Apple devices are similarly affected and others are not, this strongly suggests that the common factor is an Apple Service external to your Apple devices. A possible candidate is Apple Private Relay.

At the time of writing, Apple's Service Status page doesn't indicate a service outage:

Apple - Support - System Status

As a diagnostic exercise, having disabled (and/or removed) the VPN configuration from your Apple device(s), try disabling Private Relay. For iPad and iPhone:

Settings > [Your Name / Apple Account] > iCloud > Private Relay > Private Relay - set to OFF

The next best candidate is DNS resolution or DNS caching by your WiFi/Internet Router. You may find that a restart of your Router (clearing the Router's DNS cache), followed by a restart of your devices, will clear the problem….

To restart your router, disconnect power from the router for at least 30 seconds - then reconnect power to restart. After your router reboots (which may take several minutes), force restart your Apple devices.