I can only find a couple of recent(ish) journals on CGOAB (excluding a diary of the organised mass Cairo to Cape Town ride, which doesn't represent normality), which makes me suspect that cycling in Egypt is not very easy at the moment. Cycling down the Nile Valley was always a bit tricky, as the police tended to be worried about what would happen to you, and from time to time prevented it entirely because of security concerns, though they have also from time to time generously escorted cyclists to make sure nothing happens to them.
Here's a 4 yr old journal of cycling in N Egypt, but not down the Nile Valley, so it isn't really relevant, but I don't think you'd do that today because Sinai has become seriously dangerous.
https://www.crazyguyonabike.com/doc/?o=tS&doc_id=8900&v=J4
And, again 4 yrs old, here's a woman trying to cycle up the Nile Valley and basically finding it was impossible because she was a woman, stoned, groped, etc. She managed to join together with a local group of riders for protection for a while to make one ride. She did a bit of cycling over by the Red Sea - the police told her not to as she'd get shot, but weren't very insistent about it so she didn't believe them and lived. But in general she mostly had to take transport because of the harassment. She didn't get that police protection you sometimes read about.
https://www.crazyguyonabike.com/doc/?o=tS&doc_id=9722&v=5Q9