Q.disease on my indoor palm
At the ends of my palm leaves, there is a black oily substance. Is this some kind of fungal disease? How would I treat it?

You likely have Sooty mold on your plant, caused by insects.
Treat the plant with Neem Oil.
Check any other plants you may have in the area.
Neem Oil is organic and safe for people and pets.
https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm
https://www.gardeningknowhow.com/houseplants/palms/sticky-palm-tree-leaves-treatment-for-palm-scale.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm