Sourcing information on those involved in World War 1 Africa can cover numerous countries depending on where people were born, where resident and employed before the war, which force they enlisted with, where they resided after the war and where they died.
Below are some links to archives (alphabetical by country) which might potentially be helpful.
It is also worth bearing in mind that some archive material has over the years been destroyed by fire and other disasters. These include:
UK Burnt docs (and info on destroyed documents)
Cameroon – German documents smuggled to Fernando Po, then Spain to Hamburg and Berlin in Germany where they were destroyed in 1945 in a bombing raid. (Schulten, p234) Britain took some files from Yaunde to Lagos. These are now in the National Archive in Buea. Some records remain in the archive in Yaunde while others are in the UK National Archive.
Kenya fire in 1925 destroyed some archive material but material on World War 1 is kept in Nairobi (see Hodge’s bibliography)
Malawi while the old secretariat burned in 1919, the fire did not destroy all or even most of the First World War records. See Mel Page’s The Chiwaya War, p.236 (first edition) and pp.262-263 (second edition).
Online archival sources
The National Archives, UK on Flickr
Digitised archival collections – general
https://core.ac.uk/ eg includes 1916 German East Africa newspaper (Deutsch Ostafrika Zeitung)
Colonial archive (Archivfuhrer)
Moshi Evangelical Lutheran Church
Britain and the Commonwealth – Commonwealth War Graves Commission
Germany – Denkmalprojek – East Africa GSWA (all). Note: this is only the German army, not local forces