Do smart radiator valves work with old European radiators?

Most smart TRVs ship with M30x1.5 threaded adapters that fit common European radiator valve bodies (Danfoss RA, RAV, RAVL, Caleffi, Herz), but very old or proprietary valve bodies may need a plumber to swap the underlying valve. Check the specific adapter set included before buying, and expect that some pre-1990s valves won't accept any standard smart head.