OpenSpades is a version of Ace of Spades that is Open Source, FREE, Cross platform and easy to play.

The developers have a website here: https://openspades.yvt.jp/
And a Github here: https://github.com/yvt/openspades

Alternatively, here is a link to the original free game but its not updated anymore and is not Cross platform or Open source.
https://www.buildandshoot.com/download/

• It has players online
  
• It's FREE
  
• It's OpenSource
  
• It runs on your grandmas unbranded beige PC
  
• Unlike Call of Duty, its actually fun

Here is a link to the website:
https://openspades.yvt.jp/

Here is a link to the Download page:
https://github.com/yvt/openspades/releases


To download the game, scroll down and click on the .zip file for your platform (Windows or Apple Mac OSX)



Likely, OpenSpades is already in your default repositories.
If not, you can grab it from Flathub or Snapcraft.

Commands to install

sudo snap install openspades

OR

flatpak install flathub jp.yvt.OpenSpades