Is it true that the Companion Amr ibn al-Aas incited people against Uthman ibn Affan and boasted about his lineage with pre-Islamic pride, as stated in Ibn Kathir's "Al-Bidaya wa al-Nihaya"?

The narration mentioned in the question is weak. Al-Waqidi mentioned it in "Al-Bidaya wa Al-Nihaya" and "Tarikh al-Tabari," and he is accused of mixing the good with the bad. Therefore, his narrations, especially those concerning the honor of the Companions, cannot be used as evidence. Furthermore, the report from Ghassan ibn Abd al-Hamid, which contains an aspersion against Uthman, is from an unknown source and has a broken chain of transmission.

Lies and fabricating false reports emerged after the tribulation of Uthman's murder, may Allah be pleased with him. Therefore, it is necessary to scrutinize the chains of narration. These reports are inconsistent with the state of Amr ibn al-Aas and his jihad, as he stood by Mu'awiyah in demanding retribution for Uthman's killers. Moreover, Amr ibn al-Aas's statement in the context of death: "Then we managed affairs about which I do not know what my state is concerning them," indicates his striving and his eagerness for the truth.

Accordingly, the Companions are innocent of Uthman's blood, may Allah be pleased with him, for he was unjustly killed by barbarians and rabble, and none of the Companions participated in his killing.