An attentive survey of mainstream reference platforms, https://plato.stanford.edu, https://www.iep.utm.edu and https://www.wikipedia.org shows up that the claim that Ancient Greek philosophy was rooted in Ancient Egyptian culture have little substance. The principal support for the claim comes from the humble acknowledgement of Egyptians' aspiration to wisdom and the formative debt owed to them by some leading Greek men of letters and their visits to Egypt. Though the intellectual influence of ancient Egypt on Greek philosophy is manifest by these accounts, it should be clear that they by themselves do not measure up to being the origin or root of Greek philosophy.
An aspect of the ancient conception of philosophy is eloquently characterised by Pierre Hadot. According to Hadot, philosophy, in contrast to the contemporary view as an academic discipline, was a spiritual exercise (in a broad non-religious sense) consisting in learning to live, learning to dialogue, learning to die and learning how to read (see his Philosophy as a Way of Life: Spiritual Exercises from Socrates to Foucault, Blackwell, 1995, pp. 81–125). Hence, an ancient philosopher was the one who used to live philosophically, "sculpting one's own statue", quite unlike the contemporary scholar of philosophical discourse and theories. However, focusing only on this aspect misses another aspect which would give rise to philosophy and science as we know these endeavours today.
Another survey of the above mentioned platforms, beginning with Thales, will lay this second aspect bare, which was almost absent in the ancient Egyptian thought, whose traces were blended with supernatural or mythological elements (e.g., the god Atum, the goddess Ma'at), if there were at all. Furthermore, the first aspect was shaped by this second one in the Greek context, and its links to the Egyptian sages remain tenuous. There has not been any solid analysis that argues for a continuity between the Egyptian thought of wisdom and Greek philosophy.
Beyond any doubt, the Ancient Greeks had borrowed a lot from the peoples of other lands — Egypt, Mesopotamia, Persia ... Nonetheless, it is to downplay the originality of the brilliant leap that took place in Hellenic world, starting up in Asia Minor, to hold that it is a "stolen legacy". A helpful comparison can be the deeply incisive difference between the Egyptian employment of geometry and the theoretical character it took on in the Greek terrain.
Whether or not one is congenial to Hegelian philosophy, the following passage from his Encyclopaedia Logic (§108, Hackett, 1991) is quite illuminating to have an overall view of this historical transformation:
They [Greeks] raised the question, for instance, [of] whether one grain of
wheat can make a heap of wheat, or whether the plucking of one hair
from the tail of a horse makes it a bald-tail. Regarding the nature
of quantity as an indifferent and external determinacy of being, we
are, at first, inclined to answer those questions in the negative.
Nevertheless, we must soon concede that this indifferent increasing or
decreasing also has a limit, and that a point in the process is
finally reached where, through the continued adding of just one grain
of wheat at a time, a heap of wheat results, and through the continued
plucking of just one hair at a time we have a bald-tail.