Yes, there have been a handful of scholars who have found out information about the region's past using linguistic, archaeological and oral history methods.

For good sources to consult, I would recommend the following-

How Societies are Born: Governance in West Central Africa before 1600 by Jan Vansina, 2004. Vansina was a specialist on Central AFrica, and did much to promote the idea of using Oral Traditions in conjunction with Archaeology to explore african pasts prior to European contact. How Societies are Born is one of his more recent works, and represents developments in scholarship.

Kingdoms of the Savanna by Jan Vansina, 1966. This book is one of Vansina's more famous books, and it deals with the region of Angola and southern DRC. The scholarship is much more dated than How Societies are Born, but on the other hand you will be much more likely to find an affordable copy of it.

Joseph C Miller is another eminent specialist, focusing on the Mbundu states of northern Angola. His book Kings and Kinsmen: Early Mbundu States in Angola from 1976 would be highly relevant to your interests. However, you would want to check availability at your local library, because used copies online are pretty pricey (as are most niche academic books).

Central Africa to 1870: Zambezia, Zaire and the South Atlantic by David Birmingham extracts chapters from the Cambridge History of Africa and curates them to create a book regionally focused on Central Africa. It was published in 1981, and so reflects 1970s scholarship. So again, the same warnings about older scholarship apply.

John K Thornton has written quite a bit about the Kingdom of Kongo, Ndongo, and the Atlantic World. Africa and Africans in the Making of the Atlantic World and Central Africans, Atlantic Creoles and the Foundation of the Americas 1585-1660 (with Linda Heywood) both touch on this region, although they are focused more heavily on the post-contact period.

I know that Pierre De Maret, Koen Bostoen, Bernard Clist and others are currently doing archaeological survey work on the Kongo Kingdom. Here is the Kongoking website and here is a lecture by Maret and Bostoen concerning some of their archaeological and linguistic findings.

Beatrix Heintze is another eminent scholar who focuses on early Angolan history and anthropology. I don't know if any of her books have been translated from German, but I do know that some of her journal articles are published in English.

Aside from the books that I have mentioned, I would absolutely recommend searching JSTOR or the archives of specific journals like the Journal of African History, African Historical Review, African Archaeology Review, History in Africa, and Azania for articles by these authors.

u/Commustar lists excellent resources. But it may also be helpful to dissect your question a bit in order to focus your inquiry (and therefore the relevant answers). Here's what I mean:

"Pre European Colonization" is a fuzzy term, especially in Angola's case. It could mean before contact with Europeans, i.e., pre 1483 for the Kikongo and Kimbundu areas, or it could mean before effective Portuguese military control, or perhaps before European commercial and cultural influences began to have widespread transformational effects on the pre-existing cultures. This may seem like nitpicking, but how you answer it will lead you to very different source material.

Similarly, "the area of Angola" covers quite a diversity of cultures. You know that already, of course, but it's helpful to remember that, for example, the Ovimbundu of the central plateau were only effectively occupied by the Portuguese in the early 1900s, a far cry from the initial contacts made in the sixteenth century. So if your question about pre European colonization is open to European sources from the intervening centuries of slowly developing contact, then you have a much wider range of material available to you.

So in short, if you mean "What can archaeology and linguistics tell us (somewhat speculatively) about pre-European-contact Angola," then u/Commustar has answered most excellently. But if your question is "What do we know about the history, culture, and myths of the Angolan peoples before these were substantially altered by European domination," then there are several European sources that give a much more detailed historical insight (colored of course by their European perspective). Ethnographic studies of all sorts, collections of proverbs and myths, descriptions and even photographs of cultural activities and artifacts... If that's what you're interested in, read on.

I can only supply info regarding the Umbundu area, but maybe that will give you a start.

• László Magyar, Reisen in Süd-Afrika, 1849-1857 - primary source material from a Hungarian man who lived among the pre-colonial Ovimbundu, married an Umbundu princess, learned the language well, and wrote thick-descriptions of many aspects of culture.
• António da Silva Porto, Viagens e apontamentos de um Portuense em África - primary source material from a Portuguese merchant who settled in the area of Bié in the mid-nineteenth century, learned the language and culture, and was himself a key link in the growing Portuguese influence over the area.
• Protestant missionaries of the late nineteenth and early twentieth century were, in some cases, excellent ethnographers. Top of the list regarding the Ovimbundu was Gladwyn Murray Childs, Umbundu Kinship and Character. He notes that even in the 1930s the Umbundu culture had greatly disintegrated and changed, but his research was oriented to discovering the original Umbundu culture, myths, social structures, and language before the disintegration.
• In a similar vein, Merlin Ennis, Umbundu: Folk Tales from Angola, published 1962, preserves many oral traditions with roots back into the pre-colonial era, despite having been collected well into the colonial period.
• Linda Heywood, Contested Power in Angola: 1840s to the Present - (Secondary academic resource) Early chapters cover the social, political, and economic structures of the twenty-two Umbundu kingdoms before and during the transformations brought by trade with the Portuguese, still many years before Portuguese colonization.