@TP-Link 

Yes, all 3 plugs behave the same.

There is no vpn on the smartphone nor anywhere on the network.

I don't have an iPhone, I was referencing the instructions for manually selecting the network.  The error happens on my umidigi a7 pro and samsung tab a.

I tried with only one plug at a time, I had them all plugged in to record my screen after I gave up trying and exhausted all the troubleshooting I could find here.

I had my ISP factory reset my modem router combo device. I can now add devices using my samsung tab a. My umidigi a7 pro still does not work.

I can control the smart plugs from either device once configured with kasa.

I will test on another network, but I suspect some sort of compatibility issue with either umidigi a7 pro or Android 10/SE Linux.

I'm going to do some research, however in my experience with incompatibilities, it is best if the two vendors collaborate on specific issues.  Maybe tp-link can obtain a umidigi a7 pro 128gb model and test for themselves.  I will suggest the same for umidigi to obtain hs103 smart plugs to test with their umidigi a7 pro tip find the incompatibility.  It's also my experience that neither tp-link nor umidigi will accept these responsibilities leaving their brand tarnished in the eyes of the consumer who will likely never have a resolution to their issue.  That consumer being me in this case.  I have had success in this method with enterprise, such as dell and Intel incompatibilities.

I'll do research regarding Android 10s se Linux security and apps controlling wifi network settings. EDIT nothing obvious with quick Google search but no exhaustive reach completed

I will open a support ticket with umidigi regarding incompatibilities with smart home products. EDIT ticket open

I will also test adding the device using my umidigi a7 pro after I factory reset it now that it has updated the firmware. EDIT test failed, umidigi a7 pro still will not see devices