You've seen the warnings that you definitely can't use this QT Py with CircuitPython or MicroPython and that technically it doesn't work with Arduino either. What you can do though is use the ch55xduino board support package to write code in the Arduino IDE to compile with its C compiler.

Install Arduino IDE

The first thing you will need to do is to download the latest release of the Arduino IDE. You will need to be using version 1.8 or higher for this guide.

Install the ch55xduino Board Support Package

After you have downloaded and installed the latest version of Arduino IDE, you will need to start the IDE and navigate to the Preferences menu. You can access it from the File menu in Windows or Linux, or the Arduino menu on OS X.

A dialog will pop up just like the one shown below.

We will be adding a URL to the new Additional Boards Manager URLs option. The list of URLs is comma separated, and you will only have to add each URL once. New Adafruit boards and updates to existing boards will automatically be picked up by the Board Manager each time it is opened. The URLs point to index files that the Board Manager uses to build the list of available & installed boards.

To find the most up to date list of URLs you can add, you can visit the list of third party board URLs on the Arduino IDE wiki. We will only need to add one URL to the IDE in this example, but you can add multiple URLS by separating them with commas. Copy and paste the link below into the Additional Boards Manager URLs option in the Arduino IDE preferences.

If you have multiple boards you want to support, say ESP8266 and Adafruit, have both URLs in the text box separated by a comma (,)

Once done click OK to save the new preference settings.

Install with the Board Manager

The next step is to actually install the Board Support Package (BSP). Go to the Tools → Board → Board Manager submenu. A dialog should come up with various BSPs. Search for ch55xduino.

Click the Install button and wait for it to finish. Once it is finished, you can close the dialog.

Code Upload Options

In the Tools → Board submenu you should see CH55x Boards and in that dropdown it should contain the CH55x boards.

Under Board, select CH552 Board. Under Clock Source, select 16 MHz (internal), 3.3V or 5V. Under Bootloader pin, select P3.6 (D+) pull-up. These settings will work with the CH552 QT Py. Now you can try uploading some code examples to the board.