Srsly though: This frameset looks like it’s furnished for internal gear hub and rollerbrake only. So, quite possibly not drilled for brakes (and even if you could drill it, the drop required might be enormous...).
Edit: Front fork is drilled through, yes, but probably suits long-drop/nutted only!
maybe you could run it fixed/tireless?
Srsly though: This frameset looks like it’s furnished for internal gear hub and rollerbrake only. So, quite possibly not drilled for brakes (and even if you could drill it, the drop required might be enormous...).
Edit: Front fork is drilled through, yes, but probably suits long-drop/nutted only!