So, with Pokemon Bank closing down, a select few shiny Pokemon change from being obtainable to entirely unobtainable. Some Pokemon still become only available through Pokemon Go raids, or paid research events. That is not the focus of this post.

Which Pokemon are still obtainable after Pokemon Bank closed, but the method for hunting them becomes far, FAR slower as a result of the previous method no longer being available for transferring Pokemon into Home?

I submit the Ultra Beasts as my first guess. Soft resetting in Pokemon Ultra Sun and Moon is very fast, especially with a New 3DS or better model, and with the shiny odds being influenced by the Shiny Charm, it only takes around 6 hours or so to hit odds. However, once Bank shuts down, the only option (as far as I'm aware) for hunting these shinies down is through Dynamax Adventures in the Sword and Shield DLC. Shiny hunting a singular Pokemon in DA's is incredibly hard to approximate, but CannedWolfMeat did an appreciably reasonable napkin-math analysis for the process putting it at around 25 hours. That's a jump of more than 4x, and that's for only one of the 9 UBs in DAs you can shiny hunt! Needless to say, I REALLY want to square away these UBs for my Shiny Living Dex BEFORE Bank shuts down!

Does anyone have a different answer? I assume DA Legendaries are going to be the most common sticking point, as the time to reach odds on those is incredibly slow. I'd love to prepare a list of what Pokemon become the longest to hunt for in order, just to help fellow slow-burn Shiny Living Dex hunters who are suddenly feeling the pressure of Bank shutting down, as I am. Thanks for your time!