Thanks for your responses Bianchigirll and T-Mar. I think it's not a modified frame, the fork is OEM. There are many hybrid frames similar to this one, but all I've seen have under BB gear cable routing. Rear spacing is 130mm, no markings on steerer tube. Maybe it's not clear in the pics, but it's all welded, not brazed (except for the dropouts?).
So it's an obscure frame... perhaps time will tell what's it.