Went through this recently, needed a cheap frame quickly. In addition to the New Albion Privateer someone else mentioned, I strongly considered the Fyxation Quiver. Funky RD hanger, horizontal dropouts, and split seat stay so you can run SS, geared, or belt drive. However, I couldn't find anyone with actual real world experience. Ultimately I bought a used frame off a local Facebook swap and shop group for $250.