This will download the video and audio file seperately. But both will be in encrypted format:

yt-dlp --external-downloader aria2c --allow-unplayable-formats https://link.mpd -o fileName.mp4

Now once you have the encrypted audio and encrypted video file you'll need the key to decrypt these files. Once you have the key using the key to decrypt one at a time:

mp4decrypt --key keyFound --show-progress fileName.fvideo_avc1.mp4

DecryptedVideo.mp4

mp4decrypt --key keyFound --show-progress

fileName.faudio_und_mp4a.40.2.m4a DecryptedAudio.mp4

Now you have to merge the decrypted video and decrypted audio:

ffmpeg -i DecryptedVideo.mp4 -i DecryptedAudio.mp4 -c:v copy -c:a aac final.mp4

https://aria2.github.io/