[cornedor]

In this case, the reason might be that it needs WebGPU, which is only available in chromium based browsers. Changing my user agent doesn't let me in either. Text selection being disabled might be a "lazy" fix for text being selected while in game.

[kaszanka]

This time it's sadly just another case of a web developer who thinks he knows better than you what browser you should use, it works fine with

  // ==UserScript==
  // @name     oasis.decart.ai Firefox fix
  // @version  1
  // @run-at   document-start
  // @match    https://oasis.decart.ai/*
  // ==/UserScript==
  
  unsafeWindow.chrome = 1;