The error looks like a mismatch between expected libcrypt versions:
$ insync start --no-daemon
[28779] Error loading Python lib '/usr/lib/insync/libpython3.7m.so.1.0': dlopen: libcrypt.so.1: cannot open shared object file: No such file or directory
Arch has a libcrypto.so.2, and symlinking it appears to work okay. According to a Puppylinux thread (https://forum.puppylinux.com/viewtopic.php?t=3180&sid=9c4d39512f1e7a259953736281d1dbae&start=10), creating this symlink is or was fairly recently standard procedure on Debian for compability so it seems like it should be okay.