How to play chess variants on a mobile browser
Variants are available only on the web and cannot be played through the Chess.com apps. However, if you'd like to enjoy a variants game on your mobile device, you can do it using your device's browser!
Here's how to do it:
Go to Chess.com on your mobile browser
Tap on the hamburger menu at the top-left corner:
Tap 'Play' and select '4 Player & Variants' from the menu
Choose the variant that you want to play, customize your game, and press 'Play!'
Check out this article for more about variants: How do I play chess variants.