I got same troube but I succeed to start insync with workaround below.
cd /usr/lib/insync
sudo ln -s -f /usr/lib/libfontconfig.so.1.12.0 libfontconfig.so.1
sudo ln -s -f /usr/lib/libfreetype.so.6.17.1 libfreetype.so.6
My versions:
- 5.3.1-arch1-1-ARCH
- insync 3.0.19-1