If you can't use the horizontal dropout to achieve chain tension, there is a simple bodge that I use on my one remaining full size bike without a Chainglider:
https://surlybikes.com/parts/singleatorThe bike on which I use this is an old VTT from the early 1990's designed for derailleurs, it has vertical dropouts and no means of fitting an eccentric bottom bracket without major surgery. I use this as a visitor bike at our island flat. It has a Nexus premium 8 hub, but the system would work just as well with a Rohloff.
I fitted the Singleator pushing
up on the chain, with just enough tension to stop the chain falling off. So the extra friction caused by the one Singleator pulley is not really noticeable, in theory it should be half the friction from a normal dérailleur, maybe less as the chain doesn't bend very much.
The downsides for me are :
- one pulley to clean (trivial).
- not possible to fit a Chainglider (a nuisance because this means more chain maintenance).
There are other brands of one-pulley tensioner that would probably work just as well.
Even an old derailleur would work (done this in the past), but it was more of a hassle to set up and clean.