This is a stylized spawn effect made with geometry nodes and shader editor. There are a few parameters that you can tweak for the timing and radius of the effect. The rest is automatically calculated through the nodes.
Note:
1. Set View Transform to Standard in the Color Management.
2. Add a Glare node set to Bloom in the compositor and adjust it's parameters to get the exact look as the thumbnail.
3. Also, You Might need to increase the Max Transparency Bounces under Light Paths, in Render Settings.