Question

Is there a shiny of every Pokemon?

Answer 1

Yes

However, there is one interesting case, that being Magearna. Magearna's original form's shiny was exactly the same as the non-shiny until Pokemon Home was released. Then, the shiny color was modified to a dark gray.

Although, there are a couple Pokemon that are Shiny-locked, meaning you can only get their shiny form by hacking

List of Shiny-locked Pokemon:

• Victini
• Arceus
• Keldeo
• Meloetta
• Diancie
• Hoopa
• Volcanion
• Magearna
• Marshadow
• Eternatus
• Urshifu
• Kubfu
• Spectrier
• Glastrier
• Calyrex
• Enamorus

Source

Answer 2

Yes, every Pokemon in the game has been programmed to have a shiny form.