I don't know if the government of any African country have adopted the system of paying salaries in Bitcoin, but I know here is Nigeria they haven't, it's possible to pay employees using Bitcoin or other crypto currencies ,
With the services of some crypto currency payroll agencies like Bitwage,papaya global, ontop, which will make it possible for the government to pay their workers in Bitcoin or other crypto currencies and can be sent into their digital wallet,
Since it has to do with the government another agency can be set up in the country in respect to paying salaries as Bitcoin which will somehow help in the growth of the economy of the country.
If we want to Africa start paying salaries in Bitcoin they should expand their Internet scope cause what I know is not the majority of African people can't access the Internet tho. Rather than expecting African countries to start paying salaries in Bitcoin in a short time their people are already able to earn Crypto online in many ways and it will boost their knowledge about cryptocurrencies.