Please follow this guide at your own risk. I saw a lot of unanswered forums regarding flashing global firmware in a chinese S20 (CHC) and decided to offer my help.
I am not responsible for your damaged cause. The purpose of this guide is just to help people who can follow the steps.

Follow each step carefully

1. Download latest patched odin from here.
2. Download the latest Hong Kong firmware for S20 from here. Please note that this is latest as of writing this comment, and is for Galaxy S20 5G (G9810) only. If you own S20+, S20U, Note 20 or any other device, you can go to sammobile firmware, type your model number and get the latest Hong Kong firmware (TGY) from there.
3. Download and install Samsung usb drivers from here.
4. Kindly make sure your USB debugging is on.
5. Boot your device into download mode. If you don't know how, kindly do some research.
6. Run patched odin as administrator.
7. Connect your device to PC using original or an otherwise high quality cable.
8. You'll see "added" in the log section, indicating that your device is recognized.
9. Attach BL, AP and CP into their respective places.
10. Attach CSC (not HOME CSC) into CSC.
11. Some firmwares may include userdata, if so please attach it in userdata and if your firrmware doesn't have userdata, leave it empty.
12. Click on start and wait till its done. (If you've never flashed via odin before, I'd recommend you to watch any recent tutorial first, for general idea)

Now your device has officially moved from CHC (China) to TGY (Hong Kong). You'll have google playstore by default and no chinese bloat.