How to install a Rohloff Speedhub on a Surly Troll with rear facing horizontal fork ends
This is the answer I received from Rohloff customer support

https://www.rohloff.de/en/service/search/bike-finder/details/item/troll/


  Built of 4130 CroMoly steel, the Troll is designed as a comfortable off-road MTB/tourer. The frame feature gusseted sloping toptubes, Surly Trip Guides for running full shift and brake housing, mounts for linear-pull and disc brakes plus ample room between the stays for high-volume rubber…up to 2.75"!
  
  The Troll’s…rear load horizontals feature a derailleur hanger, slotted disc brake mounts, M10 x 1mm threaded holes for mounting the Surly Bill &amp; Ted trailer via connecting hardware (or B.O.B. Nutz), and a dedicated anchoring point for a Rohloff OEM2 axleplate. Surly designed a ton of versatility into these framesets because they wanted you to build a bike the way it will best serve you. Framesets available in sizes XS, S, M, L and XL.
  
  The Troll, requires:
  
  Disc brake use:
  
  TS DB OEM2 SPEEDHUB + special 4-bolt brake rotor + spokes with a 2.9mm neck length.
  
  Rim Brake use:
  
  TS EX OEM2 SPEEDHUB + spokes with a 2.9mm neck length.
  
  The OEM2 anchoring bolt is positioned in the additional horizontal dropout slot as illustrated above.
  
  PLEASE NOTE:
  
  2017+ Troll models will in addition, require the Surly '10/12 washers' to convert their 145mm 'Not-Boost' dropout system back to 135x10mm standard. 




And this is the answer from Surly customer support


  ... Troll’s rear dropout actually features a dedicated Rohloff torque arm slot. Our recommended set up is the OEM2 axle plate and the a Speedhub that uses the “TS” (bolt-on) axle paired with our 10/12mm adapters (below) to allow the axle to sit snugly in the Troll’s 12mm Gnot Boost dropout.  You can also get one of our Snuggnuts if you are concerned about the wheel slipping, but most of the time, the bolt on axle is sufficient.