I am looking for any kind of georeferenced data on archeological discoveries (or maybe unsuccessful expeditions) in African countries. Ideally, these would span the last 100 years and identify the location of discovery and the "discoverer".
You'll often have a hard time finding open data relatively to that, as this kind of data is generally restricted or obfuscated to limit risk of archeological looting.
For North Africa, there is the EAMENA database, which is partly accessible upon registration: https://database.eamena.org. It may not have all the data you're after, and many records have extremely sparse data (e.g. only an identifier and random approximate coordinates, no name, date, or type of site). If you're a researcher, you might get access to more data and features than what is accessible to the general public, have a look at their open data policy.
This is not my field, but given the ethical and possibly legal implications of accessing this kind of data, generally the best option here seems to be a collaboration with archeologists or organizations working in this field and area.