If you are on webOS 4 (2018-2019 sets, C8/C9), nothing here changes for you. This release is for the 2020 and later sets.
webOS 5+ can play something at last. LG deleted libAcbAPI in webOS 5.0, and that is the library the app used to bind video to the hardware plane. When the load failed the app gave up on video entirely, so every source ended in "could not open the source" — regardless of the add-on, the debrid or whether the TV was rooted. On 5.0+ the app now asks the TV's own SDL for an exported window and hands its id to the media pipeline, which is the route Kodi takes there.
Please read this before you file a bug: nobody here owns a webOS 5 set. This path is written against the SDK headers and has never run on real hardware. It may work, it may fail in a new way. The startup log now prints which path it took — [video] pronto (webOS N, acb=..., janela=...) in Settings > About > Debug console — and that line is the single most useful thing you can send back.
Known limit on webOS 5: HDR and Dolby Vision are negotiated through the ACB that no longer exists, and the replacement lives in a different media API than the one this app loads through. So playback on 5+ starts out in SDR. That is a real gap, not an oversight, and closing it means changing how the app talks to the pipeline.
webOS 4 was re-tested on a C9 (4.10.2) before this build shipped: same ACB path as before, source cropping intact, and Dolby Vision still engaging on an MP4 source.