Maybe I'm misunderstanding. Adding PNG did make the icons appear, except the favicon. That should be the one in the browser tabs and next to the url instead of the default blue and white image? Yes? It doesn't seem to change for me. Slightly off scope of the original post though.
adding .png should definitely work for the favicon too, at least it did for me, so im not sure why yours isnt. perhaps the image somehow became invalid? might be worth running through the onboarding setup again and replacing the favicon asset (then adding back .png in the admin panel after)
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Comment by bizo