I would suggest that you download your Raw DNA Data from Ancestry and upload it to Gedmatch.
FTDNA is another that does Admixture plus it has other DNA tools available but some do need a fee to unlock them.
Ancestry does have by far the largest database of DNA tests and for me they now pretty well reflect my own Admixture.  This has not always been the case and over the 8 years since I took a DNA test what has been presented has been refined as Ancestry update their algorithms. 
I have uploaded my DNA to Gedmatch, My Heritage, ftDNA and Living DNA.
My Heritage - way off the mark
ftDNA - no idea, I have not paid to unlock it, I used this company for my yDNA test.
living DNA - almost as bad as My Heritage, I am 1/4 Italian and 1/4 Irish and this site shows 0 Italian and 1/2 of what it should be for my Irish Admixture