Looks like nohup, screen, or tmux are good options.

I've used screen before, it worked well. Though I've never used it to download stuff, it should work the same

I used screen. Just start a screen session for it like "music-downloads" and then you can quit the session and exit out OR install a DE like XFCE on your server and then use something like xfreerdp to remote desktop in, run the script in a terminal on the server, then just close your xfreerdp.

I first used screen to download everything but then decided to install XFCE and Nicotine+ and just leave it up so people can download from my library also.

this was the script I used to download my youtube playlist, you can modify it to do spotify also:

#!/bin/bash  

PLAYLIST_URL="$1"  

if [ -z "$PLAYLIST_URL" ]; then  
    echo "Usage: $0 <youtube_playlist_url>"  
    exit 1  
fi  

# Log file with timestamp  
LOG_FILE="$HOME/music-downloads/download_$(date +%Y%m%d_%H%M%S).log"  

echo "Starting download at $(date)" | tee "$LOG_FILE"  
echo "Playlist: $PLAYLIST_URL" | tee -a "$LOG_FILE"  
echo "----------------------------------------" | tee -a "$LOG_FILE"  

# Run sldl with YouTube playlist  
sldl "$PLAYLIST_URL" --yt-dlp 2>&1 | tee -a "$LOG_FILE"  

echo "----------------------------------------" | tee -a "$LOG_FILE"  
echo "Download completed at $(date)" | tee -a "$LOG_FILE"  

I just ran this in a screen session. You don't have to log everything but I did it so I could check to see what songs weren't on soulseek from my playlist.

Look at the documentation on the Github-page. It looks difficult but you only need a few options and they give you examples as well.