How to access shadow dom elements in Selenium 4?

Im trying to create an automated test for login page which uses shadow dom. Im using this approach, but so far I was unable to work it out: https://titusfortner.com/2021/11/22/shadow-dom-selenium.html

Here is the login page:

<nbc-input name="username" slot="input" value="" id="username" class="hydrated">
    #shadow-root (open)
    <slot name="element-before"></slot>
    <input type="text">
    <slot name="element-after"></slot>
</nbc-input>

Here is my java code:

WebElement element = driver.findElement(By.id("username"));
SearchContext shadowRoot = element.getShadowRoot();
WebElement shadowElement = shadowRoot.findElement(By.tagName("input"));

Im getting this error:

org.openqa.selenium.InvalidArgumentException: invalid argument: invalid locator

on line:

shadowRoot.findElement(By.tagName("input"));

Im using Selenium 4.3.0, Chrome version 103.0.5060.114, and Chromedriver version 103.0.5060.134.