Set the text of a button in a more convenient and lazy way.

UGUIButtonExtensions.cs

using UnityEngine.UI;

public static class UGUIButtonExtensions
{
    public static void SetTextTMPro(this Button button, string text)
    {
        button.GetComponentInChildren<TMPro.TextMeshProUGUI>().text = text;
    }

    public static void SetTextUGUI(this Button button, string text)
    {
        button.GetComponentInChildren<Text>().text = text;
    }
}