David, a full Ashkenazi who used the pseudonym "Phyllis Sharon" but signed his real name at the end of his message, wrote here that all his recent ancestors were Ashkenazim and that National Geographic's Geno 2.0 told him he's genetically 2% "Sub-Saharan African."
Sean M. Silver, another person of Ashkenazi descent, was also tested by Geno 2.0. Somebody else presented Sean's results here, including the finding that he's 2% "Sub-Saharan African".
The genetic company 23andMe's consumer autosomal test has brought to light even miniscule genetic components that people inherited. Peter Eisenstadt wrote here: "Me, I'm, as far as I know, a pure-bred Ashkenazi Jew, which is confirmed by 23andme, which tells me than I am 93.0% of Ashkenazi descent, and a whopping 99.2% of European ancestry, with a measly 0.1% of me from sub-Saharan Africa".
Kitty Cooper wrote here that her Ashkenazic husband got tested by 23andMe which assigned him a 98% Ashkenazi score and an 0.1% Sub-Saharan African score autosomally, even in the conservative view.
23andMe also provided the autosomal results for American personalities of only recent East European Ashkenazic descent who appeared on the episode "Our People, Our Traditions" in season 2 of the PBS television series "Finding Your Roots" with Henry Louis Gates, Jr. The attorney Alan Morton Dershowitz and the playwright Tony Kushner were both reported to have less than 0.1% "Central and South African" ancestry. Many of Dershowitz's recent ancestors lived in the western Galician region of the Austrian Empire in towns that are now part of Poland. At least some of Kushner's ancestors also lived in Poland.
In August 2018, 23andMe updated their ethnicity estimates for people who tested with their v5 chip. Starting then, a small proportion of Ashkenazim show suggestions of more specific scores within the broad Sub-Saharan African category. Examples I've seen: D.R. (scores 99.6% Ashkenazic) and L.L. (scores 98.9% Ashkenazic) received 0.1% "Senegambian and Guinean" estimates, J.A. (scores 99.4% Ashkenazic) received an 0.1% "Sudanese" estimate, and H.S. (scores 99% Ashkenazic) received an 0.2% "Southern East African" estimate.
In admixture runs through Eurogenes, MDLP, and Dodecad, some Ashkenazim show small amounts in some of these tests that are attributed to Sub-Saharan ancestry, but usually well under 1% and not consistently showing across all tests, so they could be "noise", that is to say they may be elements that were assigned to the wrong ethnicity. In the comprehensive Eurogenes K36 test, Ashkenazim never show any amount of West African affinity, and almost never show any Central African or East African affinity either (not the same thing as Northeast African which is Caucasoid and does show up for some Ashkenazim in K36).
Whereas the mtDNA haplogroup L2a1c1 allegedly found in some Ashkenazim is of North African origin (I did not confirm from a reliable source that Ashkenazim ever have this), and while the Sub-Saharan mtDNA haplogroups L1 and L3a aren't found in Ashkenazim like they are in Yemenite Jews, and while L2a1a in Czechs and Slovaks came from admixture about 10,000 years ago, there is a haplogroup called L2a1l2 that some Ashkenazim belong to which is apparently of Sub-Saharan origin.
Brooke Schreier Ganz, an East European Ashkenazi with roots in Galician Ukraine, Poland, and Moldova who got tested by Family Tree DNA, wrote here that her haplogroup is L2a1l2 and "all my exact matches at FTDNA are Eastern European Ashkenazi Jewish (as am I), but just a teensy bit further up the tree, everyone listed at GenBank is sub-Saharan African or African-American." She explained here that her HVR1+HVR2 level matches for L2, L2a, and L2a1 are fellow Ashkenazim (from central and eastern Europe) whereas her HVR1-only level matches include natives of the African nations of Cameroon, Guinea-Bissau, and Sierra Leone.
Peter J. Roberts wrote here that dozens of Ashkenazim with ancestors from Slovakia, Poland, Russia, Romania, Lithuania, Latvia, Ukraine, France, and Germany carry a variety of L2a1 in Family Tree DNA's database and that other varieties of L2a1 in the database are held by tribes like the Bassa of Cameroon, the Hausa of Niger and Nigeria, the Manjaco of Guinea-Bissau, and the Kikuyu of Kenya who show as HVR1-only level matches to Ashkenazim.
In a comment here, Ted Kandell of Open Genomes wrote "mtDNA L2a1l2a A143G T14180C (with the closest match among the Pana of Burkina Faso) [...] [is] found in substantial percentages among Ashkenazi Jews."
Doron M. Behar, Michael F. Hammer, Daniel Garrigan, Richard Villems, Batsheva Bonne-Tamir, Martin Richards, David Gurwitz, Dror Rosengarten, Matthew Kaplan, Sergio Della Pergola, Lluis Quintana-Murci, and Karl Skorecki. "MtDNA evidence for a genetic bottleneck in the early history of the Ashkenazi Jewish population." European Journal of Human Genetics 12:5 (May 2004): 355-364. The supplementary data show that 1.8% of Ashkenazim possess the African mtDNA haplogroup L2a.
Marta D. Costa, Joana B. Pereira, Maria Pala, Verónica Fernandes, Anna Olivieri, Alessandro Achilli, Ugo A. Perego, Sergei Rychkov, Oksana Naumova, Jiři Hatina, Scott R. Woodward, Ken Khong Eng, Vincent Macaulay, Martin Carr, Pedro Soares, Luísa Pereira, and Martin B. Richards. "A substantial prehistoric European ancestry amongst Ashkenazi maternal lineages." Nature Communications 4 (October 8, 2013): article number 2543. The authors do not assign a geographic origin to haplogroup L2a1l but note that they found it in 1.5% of all their Eastern European Jewish mtDNA samples as a whole. They found it in 0.9% of Czech/Austrian/Hungarian Jews, 2.9% of Polish Jews, 1.4% of Russian/Belarusian Jews, and 2% of Romanian/Moldovan Jews. They also found it in 2% of French Ashkenazi Jews and 1.8% of Dutch/German/Swiss Ashkenazi Jews. They didn't happen to find it in any of their Baltic Jewish or Ukrainian Jewish samples.
Jeffrey Barak, whose ancestors were Ashkenazic Jews living in Bessarabia and Ukraine, was identified as a carrier of the haplogroup L2a1l2 by 23andMe. However, his Sub-Saharan mitochondrial ancestry, representing such a tiny fraction of his overall DNA, did not show up in the estimated ancestry composition, which reported he has no autosomal DNA from Sub-Saharan Africa.
Sandra Fishman wrote how her Ashkenazi Jewish cousin with roots from Lithuania and Latvia was detected to be a carrier of L2a by National Geographic's Geno project.
A holder of the mtDNA haplogroup L2a1f1 who is a customer at Family Tree DNA claims descent in that line from an Ashkenazi Jewish ancestor from Slovakia. L2a1f1 is also found among Spaniards and Puerto Ricans.
Some Ashkenazim, "Power77" whose paternal line is Ashkenazic from Romania and Kitty Cooper's husband among them, belong to the Y-DNA haplogroup is E1a1 (E-M44), but it is not frequent among Ashkenazim. E-M44 is found in Africa among some people in Mali and Sudan at rates of 2-5% for those countries as a whole but much more prevalently (44%) specifically among the Dogon people of Mali and even more prevalently (53%) among the Fulbe people of Cameroon. A relatively small percentage of people in countries like Morocco, Algeria, Lebanon, Spain, Italy, and the United Kingdom also have E1a1. The specific Ashkenazic branch of E1a1 which is a grandchild of E-M44 is called E1a1a1 (Z17696) on ISOGG's March 18, 2015 haplogroup tree. While some interpret E-M44 as having a Sub-Saharan African origin, ISOGG says the root haplogroup E1 might have originated in Northeast Africa despite its high frequencies further to the southwest: "E1 and E2 are found in Northeast Africa, but surveys show E1 may actually be more prevalent in Mali than in its presumed region of origin."
In a comment here, Ted Kandell of Open Genomes asserted that a small proportion of Ashkenazim belong to "a tiny West African E1b1a1a1d1a-U290 clade". I have not heard of this clade in Ashkenazim before.