A Silverblack deck must contain :
At least 60 cards only in common and uncommon rarities.
A sideboard of 15 cards only in common and uncommons rarities
Rarities :
The rarity system in Silverblack is the same as the Peasant Format, with the lowest rarity on the Gatherer.
There is no official ban list, but we can find ideas of Ban list combining the one from Pauper/Peasant and Legacy.
For example, a ban List used by an ephemeral community on discord had only a four cards Ban List :
Sol Ring
Mental Misstep
Strip Mine
Mana Drain.