Q. On Shabbos, if an individual (invited) at the meal has a dietary restriction and can only eat certain special types of bread (e.g., gluten free, spelt), should the special loaf (even if it is not whole) be placed together with the main Lechem Mishneh receiving hamotzi from the baal habeis?
What is the source for your response?
Thank you

A. Many Poskim maintain that one complies with lechem mishne even when one is unable to eat from the second accompanying chala, such as a frozen bread. (Teshuvos Vehanhogos 2: 170, Minchas Yitzchok 9: 42, Shevet Hakehossi 2: 116, Nishmas Shabbos 2: 157, et. al.). However, one should on the onset, have a complete bread of the kind he can eat.
Horav Shlomo Miller’s Shlit’a opinion is that if the baal habais is reciting the brocho and is being moitze everyone else present with his brocho, it is better that the special bread should also be placed with the others, so the brocho will be recited on it too.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a