You can include an animation of some kind, but you will most likely still need to avoid animating it via anything that references the world timers.
This, unfortunately, means no flip book animations or anything using a set timer node.
This leaves Tick, but it seems without a constantly updating widget of some kind, Tick is not called.
The solution is simple - and somewhat funny ; you add a hidden throbber.
This makes sure Tick is stilled called, which can then use to animate something else.
In then end, I used an overlay containing several image widgets each with a different frame of the ‘animation’ I wanted to show.
I then used RemoveFromParent() & AddChild() to put the frame I want to show on top of the overlay, thus animating it.
Hacky, but it works and stops the textures getting garbage collected.