Under what circumstances can apartment dwellers or anyone unable to build a sukkah be considered exempt from the mitzvah (specifically, able to eat mezonot at home)? For example, they are hungry at times that their shul or apartment sukkah is closed, or the slots for that meal are all filled. Or, should they avoid mezonot/HaMotzi all week?
If someone’s only sukkah options are sukkot where they are concerned for COVID, then they are exempt because of mitzta’eir. It is no different than leaving a sukkah because of excessive flies or bees if you are afraid of being stung. No need to avoid mezonot or HaMotzi. According to Yerushalmi (Berakhot 2:9, Shabbat 1:2) in a case of mitzta’eir for sukkah – כל הפטור מן הדבר ועושהו נקרא הדיוט.
Although that was a case where a person decided to eat in a sukkah despite that he was mitzta’eir.
Even if they would agree to eat in the sukkah, if there are no slots – what can they do? Like a normal year – if no one invites you and you have no options, you are patur.
The only question is the first night, where a mitzta’eir is chayav according to some Rishonim. But I think even for them, a chashash sakanah is different, and regardless, a person can definitely rely on the other Rishonim.