Al Kindi was a Zaydi

Abu Ishaq Yaqub Al-Kindi amongst the earliest and most famous philosophers and polymaths of Islam was in fact a Zaydi. Who lived between 158-256 AH.

There is no area that Al-Kindi did not master, the scholars of Falsafah like Al-Farabi, and Ibn Sina all benefited from the works of Al-Kindi

It is said by Sheikh Muhassan Al-Amin a great Twelver scholar of this era the only evidence on the religion of Al-Kindi was a saying from Ahmad bin Al-Nazm Al-Sakhshi as follows:

و كان المتوكل أمر بضرب الكندي سنة ٢٤٢ و كانت خمسين سوطا فضرب و كان منسوب الى الزيدية

He (Al-Kindi) was whipped with 50 strokes by the order of Al-Mutawakkil on the accusation of being a Zaydi!

Al-Mutawakil Al-Abbasi was a fierce opponent of Tashayyu in general and Zaydiyyah in particular. Ironically he is called the Reviver of Sunnah and he is respected by Ahl Al-Hadith for releasing their Imam and scholars and persecuting the scholars of Ahl Adl and Itrah.