This is a line endings issue, but not from Ubuntu. Make sure you do have node and npm installed correctly by using the command:

sudo apt install nodejs npm

Then stop Windows path variables being shared with WSL by editing the /etc/wsl.conf file in WSL. If the file doesn't exist, execute sudo touch /etc/wsl.conf first. Edit the file with the command sudo nano /etc/wsl.conf and add the following configuration:

[interop]
appendWindowsPath = false

Then restart WSL2 with command wsl --shutdown in Windows.

Note: this also affects pyenv command, see /usr/bin/env: ‘bash\r’: No such file or directory: Incompatible line-endings (WSL?)

I hit the same issue, after install nodejs and npm, just restart my wsl with wsl --shutdown solved the issue, you can try this.

This happened to me today after I updated node and npm through nvm. I realized that indeed the .nvm path was missing from echo $PATH. Then I noticed that npm use v16.14.0 would re-add it to $PATH and make npm i work again. However, this only worked for the current tab and to make it work in new sessions/tabs I had to run:

nvm alias default v16.14.0

Nodejs has been installed outside the WSL, so I typed the NPM command in the WSL window and actually called the NPM on Windows. After uninstalling both Windows and WSL nodes, I reinstalled the NODE in WSL and there is no problem

I think the better solution would be installing NOde using nvm on WSL, then you won't have this problem.

Installing Node using nvm for Ubuntu 20.04