Erel, i had to create this thread. Please test the attach file. This is an example of my project. The write permission dialog will not appear if File.WriteString(File.DirRootExternal, "1.txt", "ttt") is disabled. Try enabling it, then the dialog will appear. This is the strange issue i was experiencing and hopefully there is an explanation for this?
Test with TargetSDKVersion 29 and Android-29
Samsung S10+ with Android 10
Test with TargetSDKVersion 29 and Android-29
Samsung S10+ with Android 10