Here's my list of SS disc framesets with decent clearances, from looking for something similar:
Road steel
Genesis Day one disc
Bombtrack arise 2
Nature boy disc
Transition rapture
Omnium cxc
Surly Midnight Special
Pompetamine
MTB
Brother big bro
Kona Unit (SS version)
GT Peace
Genesis IO
Cotic simple
Singular Swift
(..loads of others probably, didn't really look that deeply)
Some of these don’t obviously have sliding or horizontal dropouts or they have thru axle which means new wheels!
I like the Omnium cxc- under 400 euro frameset seems good. Good tip that thanks
Here's my list of SS disc framesets with decent clearances, from looking for something similar:
Road steel
Genesis Day one disc
Bombtrack arise 2
Nature boy disc
Transition rapture
Omnium cxc
Surly Midnight Special
Pompetamine
MTB
Brother big bro
Kona Unit (SS version)
GT Peace
Genesis IO
Cotic simple
Singular Swift
(..loads of others probably, didn't really look that deeply)
Alu
Trek crockett / checkpoint
Arkose
Dolomite
Bombtrack outlaw
Zoulou https://www.cnc-bike.de/index.php?cPath=21_73_1232
Or any PF30 BB frame with an eccentric BB (problem solvers or ekzentriker).