Likewise, Abū Salamah—but only in al-Bukhārī’s recension.
Thus, there are now five independent chains for this ḥadīth of Abū Hurayrah, all of them authentic.
He nevertheless has other routes as well:

• Muslim, Abū Dāwūd (68), and Aḥmad (2/282) transmit it through Maʿmar, from Ibn Ṭāwūs, from his father, from Ibn ʿAbbās, from Abū Hurayrah, with wording identical to Mālik’s version.

• Al-Ṭaḥāwī (232), al-Dāraqutnī (147), and Aḥmad (2/236–489) relate it via Qatādah, from Khallās, from Abū Rāfiʿ, from Abū Hurayrah, traced back to the Prophet ﷺ, with the wording: “Whoever has prayed one rakʿah (unit) of the dawn prayer before the sun rises, and then it rises, let him add another rakʿah to it.”

• In another narration recorded by al-Dāraqutnī and Aḥmad (490) through Hammām we read: Qatādah was asked about a man who had performed one rakʿah of the dawn prayer and then the sun rose (Aḥmad’s wording: “when the rim of the sun had appeared”). He replied: “Khallās related to me, from Abū Rāfiʿ, that Abū Hurayrah told him the Messenger of Allah ﷺ said, ‘He should complete his prayer.’”

This chain is sound according to the criteria of al-Bukhārī and Muslim.

Qatādah actually possesses two further isnāds for this report from Abū Hurayrah:

(1) Through al-Naḍr ibn Anas, from Bashīr ibn Nahīk, from him. Al-Dāraqutnī and Aḥmad (2/306, 347, and 521) record it via Hammām from him, and this chain too is authentic, just like the one before it.