From LibreOffice Help
You can only animate text that is contained in a drawing object, such as rectangles, lines, or text objects. For example, draw a rectangle, then double-click the rectangle and enter your text.
- Select the drawing object containing the text that you want to animate.
- Choose Format - Object - Text Attributes, and then click the Text Animation tab.
- In the Effect box, select the animation that you want.
- Set the properties of the effect, and then click OK.