youtube-dl --extract-audio --audio-format mp3  --audio-quality  0  <Video-URL>

From man youtube-dl

-x, --extract-audio                  Convert video files to audio-only files (requires ffmpeg or avconv and ffprobe or avprobe)
    --audio-format FORMAT            Specify audio format: "best", "aac", "vorbis", "mp3", "m4a", "opus", or "wav"; "best" by default
    --audio-quality QUALITY          Specify ffmpeg/avconv audio quality, insert a value between 0 (better) and 9 (worse) for VBR or a specific bitrate like 128K (default

So your command could be as:

youtube-dl --extract-audio --audio-format mp3  --audio-quality  0  <Video-URL>

So in simple the option --audio-quality 0 is same as using bestaudio, you don’t need to use bestaudio.

Using bestaudio will obligate to download m4a, so you have to convert it back to mp3.

ffmpeg -v 5 -y -i input.m4a -acodec libmp3lame -ac 2 -ab 192k output.mp3

How to download youtube videos as a best quality audio mp3 using youtube-dl - Ask Ubuntu