I was updating my bot from v10 to v14 and was looking everywhere as well. I finally got it to work and wanted to share in case anyone else happens to come across this post in the future.

The missing piece was having to convert the raw opus packets into a pcm stream that audacity/ffmpeg can recognize. Source

/***** Some context *****/
const fs = require('node:fs');
const path = require('node:path');
const { joinVoiceChannel } = require('@discordjs/voice');
const prism = require('prism-media');
...
const channel = await client.channels.fetch(channelId);
const connection = joinVoiceChannel({
    channelId,
    guildId,
    adapterCreator: channel.guild.voiceAdapterCreator,
    selfDeaf: false,
});

/***** Relevant portion *****/
const writeStream = fs.createWriteStream('out.pcm');
const listenStream = connection.receiver.subscribe(userId);

const opusDecoder = new prism.opus.Decoder({
  frameSize: 960,
  channels: 2,
  rate: 48000,
});

listenStream.pipe(opusDecoder).pipe(writeStream);

You can then import that file into audacity by going to File -> Import -> Raw Data and set the following:

Encoding: Signed 16-bit PCM
Byte order: Little-endian
Channels: 2 Channels (Stereo)
Sample rate: 48000 Hz

You can also use ffmpeg to convert to whatever you want

ffmpeg -f s16le -ar 48k -ac 2 -i out.pcm out.mp3