After digging a bit more I found this page: https://www.cnx-software.com/2021/09/14/ch9102f-a-replacement-for-cp2104-usb-to-uart-bridge/

Looks like my M5paprer has CH9102F instead of CP2104 (as stated on the cover).
Drivers for CH9102 from https://docs.m5stack.com/en/download site works well on my Windows 8.1. So topic can be closed.

I tried the following drivers with no success on Windows 8.1:

• from https://docs.m5stack.com/en/download
  • CP210x_VCP_Windows
• https://www.silabs.com/developers/usb-to-uart-bridge-vcp-drivers
  • CP210x Universal Windows Driver v10.1.10
  • CP210x VCP Windows v6.7
  • CP210x Windows Drivers v6.7.6

On this page https://community.silabs.com/s/article/downloading-cp210x-drivers-from-windows-update?language=en_US
I found info that CP2104 should be identified as:

• Default VID - 0x10C4
• Default PID - 0xEA60

While on I connect my M5Paper on my PC via USB, I see "USB Single Serial" with:

• Default VID - 0x1A86
• Default PID - 0x55D4

Do you know where to find the right drivers for M5paper on Windows 8.1?