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.
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)
A list of references to UK National Archives Colonial Office African files can be found in an excel spreadsheet under Resources
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).
Digitised archival collections – general (including indexes)
https://core.ac.uk/ eg includes 1916 German East Africa newspaper (Deutsch Ostafrika Zeitung)
The Jean-Marie Derscheid collection – University of Florida: 3 microfilms (index)
African Pictures One to watch for photographs – has some 1914-1918 coverage eg Ethiopia
Belgium
Belgian archives
Royal Military Museum Brussels – includes information on personnel files
Foreign Affairs – includes Ruanda-Burundi from 1917
Photos of the Military campaign in Congo 1916-1918 provided by Royal Library of Belgium
Newspaper archive
Britain
The Gazette World War 1 Despatches
The National Archives, UK on Flickr
Kenya Regiment – Imperial War Museum
National Army Museum has various collections connected with Africa due to units having served on the continent.
Bodleian Library (Weston Library), Oxford, has Moyse Bartlett’s records on the King’s African Rifles, Geoffrey Hodge’s collections on the Carrier Corps and other various records from West, East and Southern Africa.
France
Inventory – Ministere des Armees. Historical Defence Service concerning Africa in WW1
Germany
Colonial archive (Archivfuhrer)
Colonial sources
Digital archive Portal
Bundesarchiv digital search (need to register to access)
German East Person database
Kenya
University of Nairobi – search German East Africa (contains Colonial Office scans covering the war years)
Namibia
Find Aid for the Secretary of the Protectorate – from 1915
South Africa
SANDF Doc Centre in Irene (near Pretoria) has personnel cards and other records – there is no online catalogue
Tanzania
Moshi Evangelical Lutheran Church
Kirey, Reginald – on Tanganyikan colonial records 1914-1960s
War dead
Britain and the Commonwealth – Commonwealth War Graves Commission
Germany – Denkmalprojek – East Africa GSWA (all). Note: this is only the German army, not local forces