Yes it is possible. Yes it is in the syllabus. Many modern aircraft do not have ADF or DME; in many of the older ones it doesn't work. Back in 1999 the UK directive was that the candidate should be able to use the Navigation equipment fitted to the aircraft. There is no precise clarification, it would only make things more restrictive. With the decomissioning of NDBs and VORs scheduled in the near future it will only make things worse. There are numerous ways of teaching these aids on the ground, the Skill Test requires only demonstration of navigation aids; so long as you can do that you don't specifically need ADF or DME.