Here is a comprehensive guide on handling Language Strings in The Sims 4.
To ensure text appears regardless of the player's language setting, use Tools > Modding > Copy string tables to all languages . Using STBL Editor & S4PE
Depending on your needs, you can use specialized tools to manage these updates. Using Sims 4 Studio (S4S)
A "language strings update" (language strings upd) for The Sims 4 is a content patch that modifies the game's localized text resources—UI labels, tooltips, interaction names, dialog, notifications, cheat strings, tuning descriptions, and other in-game text—without changing core gameplay binaries or large asset bundles. These updates are commonly used to fix typos, improve clarity, add new localized content for recent features, or enable new debug/cheat options across languages.