Q. Is this (the seuda on the third day after the bris) a seudas mitzva?

A. See on the prior two questions that Poskim disagree on this. In general many Chassidic traditions give great importance to this seuda (see Shem Mishmuel – Vayeshev 697, Avodas Yisroel – introduction, Imrei Emes – Likutim p. 96 et. al.) that consider this banquet to be tantamount to receiving the Shechina, as it was in the seuda of Avraham Avinu. It is then that the Patriarch prayed to Hashem that He should remain with him, meaning that Hashem should always be present at this seuda for all generations to come. (Lev Simcha – Devarim p. 79.) It is said that the Bais Aharon of Karlin when about to attend this seuda would call out “ I am about to receive the presence of the Shechina” (Al Pi Hatorah p. 177 n. 116)
Horav Shlomo Miller’s Shlit”a opinion is that in order to comply with the widely divergent opinions, Divrei Torah should be said in order to make it a certain seudas mitzva.

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