@wolfplanetzero, @gigiv, @blm1007blm1007 and everyone else interested in this discussion - I took a minute this afternoon to go back and find the original research - in 1985 - that led to this original concept for treating NTM/MAC.
https://journals.asm.org/doi/epdf/10.1128/aac.27.4.485
What I would like to point out is that garlic was use to treat M tuberculosis back in the 1930's and 40's, before the development of antibiotics, but the efficacy wasn't really tested.
Here is what the authors concluded:
"Whether garlic extract has any future in treating human mycobacterial infections remains to be evaluated. If the invitro studies of the inhibitory power of garlic extract against mycobacteria can be interpolated, it may be surmised that very high levels in serum would have to be achieved. These high levels could be toxic to the -SH groups of the animal or human being treated. Further studies in animals are indicated to determine achievable safe blood levels and overall toxicity. It is conceivable that smaller amounts or garlic extract along with other standard antituberculosis drugs may act synergistically against mycobacterial infections."

A deep dive into Google Scholar did not uncover any new research specifically on NTM/MAC but it did uncover this great review of the study of the potential uses of allicin in medicine.
https://www.mdpi.com/1420-3049/26/6/1505
Three interesting findings:
- Only raw garlic counts, as allicin is destroyed by heat.
- "Allicin taken up by cells, or entering the bloodstream, reacts readily with GSH in competition with cysteine residues in proteins. For this reason, it is difficult to envisage being able to achieve a therapeutically relevant concentration of allicin in cells anywhere in the body by simply swallowing it. "
- ...allicin is an irritant which stimulates pain-sensing neurons, and self-medication has led to a spate of reports of self-inflicted harm [21]. Thus, while small amounts are prized in culinary contexts, over-exposure to allicin is clearly harmful."
-"Perhaps, after further carefully controlled research and all necessary precautions, a pulmonary exposure route for allicin vapor might be able to be developed under appropriate circumstances to achieve therapeutically effective concentrations in the lungs."
"...A recent survey showed that several lung-pathogenic bacteria, including MDR strains, could be inhibited in vitro by allicin vapor and the aerodynamic behavior of allicin aerosols and vapor has been investigated in a lung model, thus allowing some preliminary determination of dosage and synergy without the need for animal experiments [88,98,99]. Nevertheless, progression to the next stage will require carefully controlled, ethically sound animal experiments before therapeutic protocols for humans can become feasible."

So, we appear to be left with the old, tired "more research required" in addition to the caveat that directly inhaling garlic fumes, where the demonstrated benefit lies, can be dangerous.

"Food for thought"? I need to give my healing shoulder a rest now