If they did it for Telegram desktop then it must be possible, right? Just a matter of how.

There's a few ways to do this.

You can use the autofocus attribute as Ram mentioned in the comment. Simple, but I like to avoid HTML attributes for this kind of DOM manipulation because you're at the mercy of the browser understanding and implementing the attributes.

You can also give it a tabindex 1, but that means you'll have to keep track of your tabindexes for all focusable elements.

You can also write up a quick function under document ready like

$(document).ready(function() {
    $('#InputFieldID').focus();
});

These are only a few solutions I could think of off the top of my head.

The simplest way is this:

document.getElementById("myInput").focus();
    document.getElementById("myInput").addEventListener("blur", (e) => {document.getElementById("myInput").focus()})

<input id="myInput">

I hope I helped you