Bit of a controversial and unpopular opinion but I see Krishna as a brilliant human
I'm an avid reader of history and I do consider the inner(probably lost) layers of Mahabharata as something that did take place historically because there is some literary evidence of Kuru Kings before and after the conflict period such as Dhritrashtra Vaichitravirya, Parikshit, Janamejaya. However, there is absence is of Kings in the MBh. The Kuru Polity as we know it shaped Vedic era and promoted it.
Krishna's role is the most intriguing for me in the MBh. If I view from a strictly historical and logical sense I cannot accept incidents such as Vishwaroopa in Sabha or on the battlefield as absolute ground truth. Krishna for me is an actual Vedic-era hero who played a gigantic role in shaping the Kingdoms of that era. For me he is someone with immense knowledge of dharma, a brilliant strategist, statesman and someone who rose to a great status in Chandravamsha lineage specifically for the Yadavas. Vasudeva Krishna of history did exist for me but I may not accept him as the Supreme Godhead and the origin of the universe.
There is also a mention of Ghora Angirasa as the teacher of Krishna Devakiputra in the Chandogua Upanishad but he does not get a mention in the MBh(ofcourse since it does not centre around Krishna) or his childhood although explains the reason the initial 3-4 chapters of Gita focus on dharma karma and yoga through some sort of "upanishadic lens".
His childhood is also absent from the Mahabharata and Harivamsa was developed way later. It might incorporate his actual childhood passed within the Yadava clan but got exaggerated to an impossible extent which is the same for Mahabharata which was developed through layers which made it evolve from a bard of dispute to a grand encyclopaedia. The core of Mahabharata involves a 100% true story for me even if there is no archaeological evidence but enough literary evidence.
Link: https://hindupedia.com/en/Ghora\\\_%C4%80%E1%B9%85girasa