Android: debugger is not working on Emulator

1. Create an empty Qt Quick application project.
2. Add a breakpoint in main.cpp
3. Run under debugger. Result: it shows error messages. Android app is waiting for the debugger to attach.

Error message box in Qt Creator:

---------------------------
Failed to Start Application
---------------------------
Connecting to remote server failed:
Remote connection closed
---------------------------
OK
---------------------------

In Application Output:

killall: gdbserver: No such process

rm: /data/user/0/org.qtproject.example.untitled2/debug-socket: No such file or directory
07:51:02: Debugging "-qmljsdebugger=port:63886,block,services:DebugMessages,QmlDebugger,V8Debugger,QmlInspector,DebugTranslation" ...

Screenshot of my Android settings tab is attached.

 Sometimes it also says:

07:56:01: Cannot find C++ debug server in NDK installation.

All above is for Qt 5.15.2.

If I try Qt 5.12.11, I get this message:

killall: libgdbserver.so: No such process
rm: /data/user/0/org.qtproject.example.untitled2/debug-socket: No such file or directory
08:01:58: Debugging "-qmljsdebugger=port:49852,block,services:DebugMessages,QmlDebugger,V8Debugger,QmlInspector,DebugTranslation" ...
Could not load shared library symbols for 262 libraries, e.g. /system/lib/libandroid_runtime.so.
Use the "info sharedlibrary" command to see the complete listing.
Do you need "set solib-search-path" or "set sysroot"?

I've also attached some logs.