Is there a single term for who have sex with non-living things?
People who derive sexual satisfaction from inanimate objects are referred to as objectum sexuals.
Paraphilia is the common term for all abnormal love, including that with inanimate objects. The Greek suffix -phile is also used to describe someone having sex with an object (i.e. zoophile = someone who has sex with animals). So you could describe someone having sex with non-living things as a paraphile.
I think the word is just masturbation - a common form of autoeroticism, providing sexual pleasure or orgasm in the absence of a partner.
Wikipedia defines even a blow-up sex doll as aid in masturbation, so unless by "non-living" OP means "dead" (in which case it's necrophilia), anything inanimate involved in "solo sex" is a masturbatory aid and/or the object of a fetish.