Black Powder & Dark Magic
All classes available in the Players Handbook are open to play as well as these additional ones.
If your class proficiencies grant you proficiency in a ranged weapon, players can swap one ranged weapon out for a firearm of similar properties.
For characters who wish to multiclass as a gunslinger, the minimum ability score to do so is Dexterity 13.
Further, when you multiclass into the gunslinger class you gain proficiency in firearms and gunsmith’s kits.
Multiclass gunslingers with the Spellslinger feature add one third of their levels (rounded down) when calculating their available spell slots.