Hello, I'm developer of NanoVNA Web Client.
I've noticed that the latest Chrome for Android has bugs around WebUSB that prevent the application from successfully getting a USB device.
This motivated me to create and test an Android version that does not rely on WebUSB or WebSerial around serial communication.
It will also be available on the Play Store, but it is still under review and cannot be downloaded from there.
However, the version whose signature is different from the release version can be downloaded as "nightly" from GitHub's Releases page. If you need it, install it and try it out.
cho45