Unity WebGL : HTML elements are freezing while Unity is loading

Hello everyone !

I am working on a WebGL game and at the moment it loads reasonably fast. To start playing my game players have to go through an UI to create rooms and manage their settings.

At the moment this UI is created in unity but to improve the experience, I wanted to try moving most of the UI in HTML and javascript code. This way players could do most of the stuff that happens before playing right away while the actual game is loading in the background.

I tried to do this, starting with a really simple HTML/JS UI but while the game is loading it is slowing the whole page and the UI is really difficult to use.

I am guessing that it is caused by the CPU consumption of the UnityLoader, is there a way to make it less resources hungry or to prioritize the rest of the page over it so that it doesn't freeze? (Even if it makes the loading go more slowly)

If you can think of any other way to do what I am trying to accomplish (allowing the players to start interacting with my game as soon as possible) I am also interested :)

Thank you, please tell me if that wasn't clear or you need more information !