UTF-8 is the important clue
M3U8 conventionally identifies an M3U-style document encoded as UTF-8. That makes multilingual channel names and paths predictable across systems. The extension alone does not say whether the file is a television channel directory or an HLS manifest.
Two common jobs for similar text
A directory playlist can list many unrelated channels. An HLS manifest instead describes one adaptive stream: a master manifest lists quality variants, while a media manifest lists timed segments. Both can use .m3u8, so inspect the tags and context rather than guessing from the filename.
Quality is decided elsewhere
Resolution, bitrate, codecs and segment health determine the viewing experience. Renaming .m3u to .m3u8 cannot improve a source. Convert encoding deliberately, preserve line endings where required and test the referenced media separately.