In Generation 8, the odds of a Pokémon being shiny when hatched from an egg with the Masuda Method and Shiny Charm are 1/512
For additional info (not directly answering your question), with just the Masuda Method, the odds are 1/683, and the odds with just the shiny charm, they are 1/1365
Please note: These are rounded to the nearest whole number.
Source
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