Using Quartus 19.1 Lite on Windows 10 - Platform Designer failed when executing "Generate HDL". Appears that command "wsl" is missing?

I had the same issue. I did 3 things before I started working with Q19:

#1 enabling WSL in Win 10

Install WSL (Windows Subsystem for Linuxs), in Power Shell (as administrator) execute:

dism.exe /online /enable-feature /featurename:Microsoft-Windows-Subsystem-Linux /all /norestart

and Reboot PC

#2 install Ubuntu in Windows environment, run power shell as admin and:

i) Invoke-WebRequest -Uri https://aka.ms/wsl-ubuntu-2004 -OutFile Ubuntu.appx -UseBasicParsing
ii) Add-AppxPackage .\Ubuntu.appx

Next, from menu start run "Ubuntu"

After this step, you should have console with Ubuntu session. You can open new window by running "Ubuntu" from Menu start. This is Ubuntu, so you can download any package as you need.

#3 install additional package in Ubuntu:

sudo apt update

sudo apt install wsl

*remark - remember about proxy. If your network requires special settings, please apply them in your Ubuntu session (/etc/apt/apt.conf.d/)

After all of theses step I could use my quartus in Windows.

#2