I know the ulta wormhole increases shiny chance; I already got modest shiny altaria in a luxury ball and shiny sigilyph. I also know that shiny chance is predetermined (meaning a wormhole with shiny sigilyph will always have shiny sigilyph, which helps with nature soft resetting and catching perish song altaria). But exactly how much does each level of wormhole increase the shiny chance? btw I don't have a shiny charm.
Here's the max chance each portal can contain a shiny Type 1 - 1% Type 2 - 10% Type 3 - 19% Type 4 - 36% (With shiny charm sorry for without shiny charm it should just be whatever divided by about two) Source: https://www.serebii.net/ultrasunultramoon/ultrawormholes.shtml