I honestly don’t know where to categorise this honestly.
Normally, when one tunes to an NDB, it would switch directly to ADF5 with no ability to have a localizer on its own. A few days ago on approach to Zagreb(LDZA), one of the procedures of the STAR I was flying was to intercept a radial for the ZAG VOR. ZAG VOR is right next to ZAG NDB. The ZAG VOR was glitchy and unable to set up NAV1 and NAV2, meanwhile, the NDB set up ADF1 and ADF2 in place of the NAV1/2 with their full functionalI ties enabling me to intercept a radial to an NDB. I don’t know if this is the usual since I haven’t experimented with NDBs much, but what a surprise.
NAV2 engaged is the supposed ADF2 for the ZAG NDB.