Where & how to dispose of non-working hot tub?

Have you tried a thrift store? Some will pick up some items. You should have had the previous owners take it with them!

A reciprocating saw and some heavy duty contractor bags

Angle grinder is highly recommended for fiberglass tub, with lots of appropriate safety gear including having water nearby. Trash or recycle the cover. Use wood surround for charming enclosed garden safe from bunnies, etc.

If preferable, make the surround a raised-Bed by collecting lots of plastic bottles sans lids until it’s shallow enough to be comfortable to plant. Cover the bottle with the sturdy liner which you can screw or staple to the inside, then load in dirt.

I'd recommend cutting it apart yourself and putting the pieces out with your trash. It might take a couple weeks to get rid of it if you have a trash limit.

Try Craigslist again. Depending on where you're located, people may not be thinking about hot tubs if they are still shoveling snow.

advertise on gumtree as a giveaway eric

do not cut up with an angle grinder as the dust is dangerous to you and others in the wind

If you cannot get rid of it as a dead hot tub, what about "selling" it as a free in-ground koi pond?

https://davesgarden.com/community/forums/t/893810/

http://homeguides.sfgate.com/turn-spa-pond-101234.html

https://www.pinterest.com/pin/527273068847321983/?lp=true