Garlic substitution in marinade/paste

I’m trying to find a substitute for garlic in a chicken pulao recipe. The masala paste calls for 4 cloves of garlic, which are ground with the other ingredients into a paste. I’m already substituting radish for the onion. (My sister has celiac disease and is very sensitive to/finds it difficult to digest onions and garlic and related — no chives, shallots, etc. Even garlic and onion powder are out.)

I’m not sure what to substitute here. If it was a small quantity, such as one clove, I’d be ok in just omitting it entirely. But 4 cloves is not an insignificant amount. Further, the canonical ‘onion and garlic subsitutions’ question suggests a lot of other ingredients still in the garlic/onion family — which are all out. Asafoetida, which it suggests, I’ve only ever used as an onion replacement. And even in that other question it says to fry it in hot oil first. My current use is as part of a paste which is used to marinate the meat overnight prior to cooking so I’m not not sure how having to fry it in hot oil first would work into that (assuming I can even find it in a store.)

I don’t want to use ginger since the paste already includes ginger. Can I use horseradish? Garlic adds a certain kind of ‘umami’ and sharpness/pungency that I’m unsure how to replace in a marinade like this.

Basically the recipe is to grind a bunch of ingredients into a paste, coat the chicken, and let sit overnight. The coated chicken is then cooked with rice and spices to make the pulao. The other ingredients in the paste are onion, ginger, yoghurt or buttermilk, and spices.