There may be stations outside the major cities that are still on FM only, but it can't be a huge number at this point.
Here's a presentation from Norway's broadcast licensing authority dated July 2022. Statistics about local radio are on page 30 through 33. They note that, as of February 24, 2022, the local radio market in the country consisted of 232 FM licenses and 330 DAB licenses, of which there were 160 licensees.
Page 33 shows the breakdown of licensees by method of broadcasting. 70 broadcast only on FM, 26 only on DAB, and 64 on both. The number of FM licensees increased from 2021 to 2022 because it's still possible to get an FM license outside of Norway's four largest cities (Oslo, Bergen, Stavanger, Trondheim).
There's also this statement on page 33:
Inntektene i lokalradiobransjen kommer i all hovedsak fortsatt fra FM. DAB-sendingene finansieres i stor grad av inntektene fra FM-sendingene, fordi det så langt har vist seg vanskelig å finne bærekraftige driftsmodeller for rene DAB-lokalradioer.
Translation:
Revenues in the local radio industry still primarily come from FM. DAB broadcasts are financed in large part by the revenues from FM broadcasts, because it has so far proved difficult to find sustainable operating models for purely DAB local radio.
Another good source of information is the
Norsk mediebarometer, published annually by Statistics Norway. Data on radio through the year 2021 start on page 37 of
the latest edition. There was a small, but noticeable, dip in radio radio listening immediately following the national networks moving to DAB, then a more gradual decline after that, mainly because radio use among the 16-24 age group--and to a smaller extent the 25-44 age group--is in free fall, although that process was underway before the move to DAB (see fig. 7). Local radio saw a modest increase in use in the year after DAB but then soon went back to its long-term average.