wsl-notify-send

https://github.com/stuartleeks/wsl-notify-send
https://stuartleeks.com/posts/wsl-github-cli-windows-notifications-part-1/

Prequel:

Make a folder, say C:\bin
Add that to the user windows %PATH%
from cmd, check path with: echo %PATH%
put wsl-notify-send.exe there

How to add folder to Path illustrated.

Example:

As seen from Debian:

wsl-notify-send.exe --category $WSL_DISTRO_NAME "done calculating"

A begining of a nice function is on the page:

notify-send() { wsl-notify-send.exe --category $WSL_DISTRO_NAME "${@}"; }

p.s. Real one should include linux version as well.