The .srt format is the most widely compatible. If your file is in .ass (Advanced Substation Alpha), it may include custom styling that some older smart TVs cannot display properly. How to Use
Download from OpenSubtitles which offers versions specifically tagged for "BluRay x265". subtitle Undine.2020.GERMAN.1080p.BluRay.x265-V...
Because this is a GERMAN BluRay release, it typically runs at 23.976 fps . If you notice the text drifting away from the speech, ensure your player isn't forcing a different frame rate. subtitle Undine.2020.GERMAN.1080p.BluRay.x265-V...
Alternative SRT files are often available via Addic7ed for multi-language support. subtitle Undine.2020.GERMAN.1080p.BluRay.x265-V...