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You got me curious so I looked at asset from Unity Store and there is quite some:
There is free ones like https://assetstore.unity.com/packages/tools/particles-effects/gater-portals-system-59185
This one seems really great (but not free) and can play on scale (spoiler for FoE episode 2 ...), and there is a demo only
https://assetstore.unity.com/packages/tools/particles-effects/portalkit-pro-vr-a...
Even if you don't use Unity, it can be great for learning. I saw video of Memory of a Broken Dimension but did not know it was out, I need to try it!