LG runs two separate webOS lines, and the distinction decides whether this route works for you.
webOS TV
Supported. This is the consumer television line, and Screenly runs through the browser built into the set.
webOS Signage
Not supported. This is LG’s platform for business and industrial displays, also sold as webOS for Pro or Commercial. If you run these, tell us which models and how many.
Note
LG and Samsung are currently inverses of each other. On LG we support the consumer line; on Samsung we support the commercial range. Check which line your model belongs to rather than assuming the pattern holds across brands.