Support depends on which Samsung line the display belongs to.
Commercial displays
Supported. These are the panels Samsung sells under the Smart Signage Platform, commonly written as SSSP.
Consumer televisions
Not supported. Consumer sets do not allow custom app installation, so there is no way to install Screenly on them.
Use a separate device over HDMI instead, such as a Fire TV Stick or an Android box.
Note
LG and Samsung are currently inverses of each other. On Samsung we support the commercial range; on LG we support the consumer line. Check which line your model belongs to rather than assuming the pattern holds across brands.