Obviously this is a pretty fringe corner case but a Genasi should be able to use their CON to cast spells from items that allow the spellcaster to use their own casting stat instead of defaulting to a +0. Relevant rules from chapter 7 of the DMG
A magic item, such as certain staffs, may require you to use your own spellcasting ability when you cast a spell from the item. If you have more than one spellcasting ability, you choose which one to use with the item. If you don't have a spellcasting ability - perhaps you're a rogue with the Use Magic Device feature - your spellcasting ability modifier is +0 for the item, and your proficiency bonus does apply.
and racial traits of Fire Genasi (though other Genasi have this error too)
Reach to the Blaze
You know the produce flame cantrip. You can cast burning hands (2nd) once per long rest. CON is your spellcasting ability.
Obviously this is a pretty fringe corner case but a Genasi should be able to use their CON to cast spells from items that allow the spellcaster to use their own casting stat instead of defaulting to a +0. Relevant rules from chapter 7 of the DMG
A magic item, such as certain staffs, may require you to use your own spellcasting ability when you cast a spell from the item. If you have more than one spellcasting ability, you choose which one to use with the item. If you don't have a spellcasting ability - perhaps you're a rogue with the Use Magic Device feature - your spellcasting ability modifier is +0 for the item, and your proficiency bonus does apply.
and racial traits of Fire Genasi (though other Genasi have this error too)
Reach to the Blaze
You know the produce flame cantrip. You can cast burning hands (2nd) once per long rest. CON is your spellcasting ability.
Obviously this is a pretty fringe corner case but a Genasi should be able to use their CON to cast spells from items that allow the spellcaster to use their own casting stat instead of defaulting to a +0. Relevant rules from chapter 7 of the DMG
and racial traits of Fire Genasi (though other Genasi have this error too)
A sample character with the erroneous behavior can be found at https://www.dndbeyond.com/characters/4487235/UtiyS1
Can confirm this one, and it’s still not working. Racial Spellcasting Modifiers aren’t being considered.