Ott reports intranasal and sublingual use of 5-MeO-DMT freebase, so I guess a salt isn't strictly required. I've never tried that myself. I'd guess the salt would at least be less irritating.
5-MeO-DMT salts have a reputation as hard to crystallize, and that may explain your failure. The oxalate is reportedly easiest, and I
succeeded with that. I'd guess that would also be irritating though. I guess that reddit procedure chose the 1:1 succinate based on the Usona Institute's
paper, which does say it precipitates from acetone (and gives lots of solubilities and other properties in the supporting information; they indeed suggest hot ethanol for crystallization). I tried their methods, but all my attempts failed. That might have been residual water like
@Transform says, since my extract wasn't dried under vacuum and I worked in open air vs. their big rotovap. It might also have been the different impurity profile of my natural product vs. their synthetic. Beckley Psytech is running trials with the benzoate, which I haven't tried.
I'm not sure there's actually any need to crystallize, though? I've consumed mebufotenin-dominant
Phalaris extracts intranasally and sublingually in liquid form, just by dissolving in water and citric acid to pH ~ 5. I don't think there's much history of such use, but it seems relatively safe to me (considering the tryptamines alone; other constituents of the crude plant alkaloids will at least temporarily impair your sense of smell, so purification is advised).
Note the general danger of this drug. Many serious overdoses are reported, including at least one death.