What is this African bug?

Based on the long legs and long antennae, I'd say you're correct that it's an orthopteran, very likely a cricket or one of its allies (i.e., suborder Ensifera).

Within this subgenus, the most likely candidate families are either the "true crickets" (Gryllidae) or "camel crickets" (Rhaphidophoridae).

Your photo is not nearly good enough to begin making more informed specific guesses. However, If I had to guess, it could possibly be a cricket in the genus Phaeophilacris, which are striped-leg crickets found in Africa.

• See inaturalist for incidence of this genus in Africa.

You can see some photos of Phaeophilacris Bredoides here, with a few photos copied below:

^Source

You can read an interesting paper about communication in this genus here¹

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^{1. Heinzel, H.G. and Dambach, M., 1987. Travelling air vortex rings as potential communication signals in a cricket. Journal of Comparative Physiology A, 160(1), pp.79-88.}