TL;DR — webOS's WebAppManager engine resolves the default Intl time zone to Etc/Unknown, which ICU formats as UTC. Date is perfectly correct; only Intl is broken. jellyfin-web renders every clock through Intl, so they all shift together by your UTC offset. Nothing about your TV, server, or container time zone is misconfigured. Fix: pin the zone from JavaScript (webos-intl-timezone-fix.js).
In the Jellyfin app on an LG Smart TV, every rendered time is behind (or ahead) by exactly your UTC offset: