Two treatments I've heard of through unverified interwebs:
Ivermectin (yeah I follow that guy's YouTube, there's lots of study about it but afaik the usefulness for smell loss in particular is anecdotal). The mechanism would likely be that it clears out residual viral particles/pieces of cellular garbage that are causing damage.
LSD (apparently a small dose helped a guy? I think this story is on Zvi's latest covidpost.) Obviously a lot more risk with this one and I would guess it could only work by increasing sensory output because psychedelics. (This kinda tracks with the essential oils suggestion? Sniffing stuff a lot could rewire some neurons I guess.)
Good luck!
Sniffing strong essential oils seems to have helped me regain at least some of my smell and taste
I just started added massive quantities of the few things I could still taste/smell (in my case this meant a lot of ginger and chili pepper) until my sense of smell came back.
My friend had COVID in September 2020 and never got her taste back. What low-risk random things should she try doing to get it back? Recommendations need not be backed by anything stronger than “a friend of a friend heard…” or “I saw it on TikTok” - I’m looking for a broad library of things for her to consider trying. She is sane and is not the type to drink bleach or whatever, so don’t worry about recommending questionable things.