Besides hieroglyphs and derivates, assuming Egyptians weren't influenced by Sumerians?
The Dogon people have a system of symbols/pictographs for divination purposes, and some other groups have something similar. Not writing yet, but look at the Chinese.
Nsibidi is really curious, maybe it's an actual writing system, who knows.
>it seems to be closer to something like the runic alphabet than an actual system of writing.
What do you think runes were? Also Nsibidi is not even remotely an alphabet.