The JP-QR701 specifications indicate that it has GB2312 support. I think this also applies to similar products that all seem to come from the same OEM or at least from the same design.

Most documentation - especially that found on English-language distributors - is however lacking
in any detail on how to use the Chinese language support.

After a bit of digging around, I eventually found some documentation on
the OEM 厦门精普电子科技有限公司 Xiamen Jingpu Electronic Technology Co Ltd site
that revealed the trick - specifically the QR701 Module Instruction Manual.

It doesn't use the standard character set / code page instructions, but rather uses two additional commands to enable/disable Chinese language support. When Chinese language support is enabled, 2-byte GB2312-80 characters can be written to the printer.

• `FS &` - Set Chinese Character Mode
• `FS .` - Cancel Chinese Character Mode
• where FS is "Field Separator" chr(28)

See the web page for the project repo for more details of the build, including full code and schematics.