For some reason, the integration of Librespot in Hutspot doesn’t work anymore, I have also had issues with this, even on the 32-Bit version.
However, there is a simple solution: just start librespot from the Terminal everytime you want to use Hutspot.
I personally have written a small Bash-Script for that, so I don’t have to type the whole comman everytime. I have used this command to start Librespot:
librespot --cache /home/defaultuser/.cache/librespot --username <Your Username here> -b 320 -n Xperia10III --backend pulseaudio
(Sorry for the bad formatting, I am writing this on my phone)
You can of course customise the command to your needs, for that I recommend reading the official Librespot-Docs.
After you have executed the command in the terminal, switch back to Hutspot and you will see your device in the devices-section