Run the following command to install the 32 bit libraries for Mint 21 to be able to use Vivox correctly:
sudo apt install gstreamer1.0-pulseaudio:i386 libidn12:i386 libuuid1:i386 libstdc++6:i386
Navigate to the directory that contains libidn12:i386
cd /lib/i386-linux-gnu
Verify you have libidn12 installed by typing
ls -l libidn12*
Create a symbolic link IN /lib/i386-linux-gnu:
ln -s libidn.so.12.6.3 ./libidn.so.11
Restart Firestorm