Ideally yes one must eat bread, however, if it is very difficult for you should not eat the seudah because of this and just eat meat and wine.
Explanation:
It is very important to wash and eat bread by Seudat Shabbat.
The Gemara Shabbat 117b: The Rabbi Taught-How many Seudot is one required to eat on Shabbat? Three. R’ Chidka said “four”. R’ Yochanan said they both based their opinion on one passuk,” And Moshe said eat it (the Man) today because Shabbat is day or Hashem, you should not go out to the fields.” R’ Chidka understood it says Yom three times for three Seudot, three during the day excluding night.
The Shulchan Aruch (274:4) ruled: The night Seudah and the morning Seudah one is required to eat bread.”
The Rashba says that it is because of the passuk “Vkarat L’Shabbat Oneg” and Oneg is only with bread
Seudat Shlishit one may eat without bread if he is still very full.
By Seduat Purim:
The Meiri writes (Pesachim 68b) The is no Kviat Seudah without bread.
The Rosh (Berachot Shlosha SheAchlu 23) one is required to eat bread on Yom Tov because it says simcha. Purim is also a day of Mishteh Vsimcha so yon ed o eat bread.
So ruled the Mor Uketziah (695) so rule the Aruch HaShulchan that one does not fulfill his mitzvah of Seudat Purim without bread.
ON the other hand, the Magen Avraham (695:9) write that we don’t find anywhere which say on needs to eat bread on Purim. So writes Elya Rabah and the Bigdei Yesha. So, writes the Shaarei Teshuva and the Kaf Hachaim that one fulfills his Mitzvah of Seudat Purim without bread.
Since it is a machloket it’s better if you can eat bread by the seudah. So ruled R OY (Chazon Ovadia Hilchot Purim Simchat (Yom Hapurim 1)
