Do you have any sources or leads regarding this point? I'm interested to find out more about it. As far as I knew, Portugal was not interested in relinquishing its African colonies, especially not Angola, which as more "reliable" than Mozambique.
On the OP, I think the Netherlands could have been a much better contender than, for example, Belgium, in the late 19th Century. They had the Dutch Gold Coast (Guinea), but sold it to Britain, and in the early 18th Century had lost colonial outposts in eastern Africa (in Maputo Bay and the island of Mauritius). If you reverse these losses, coupled with a surviving Dutch Cape Colony, we might see interesting developments in a south-African focused colonial empire.
Austria always seemed much more concerned with European affairs than overseas' adventures, but I believe that they could perfectly outfit an official (even if privately-coordinated) expedition to somewhere in Africa or even India - as many countries actually did - before the UK gets busy in the east. This would make the Croatian and eastern Italian ports the gateways to their colonial empire. Perhaps they try to penetrate in Tunis, Libya and Egypt as means of thwarting the Ottoman domination in the eastern Mediterranean.
Also, we can always have Spain be more participative in the Scramble for Africa. For a country that once held the largest colonial empire, they got a really poor share of Africa during the 1880's. A stronger Spain (perhaps one that avoided the Carlist Wars) might put a more serious effort to conquer western Africa, possibly even anticipating the French annexation of Algeria.