I’ve tested this, and I get the same issue on nixos, and using the LD_LIBRARY_PATH=/nix/store/rlvhxcqirgl38iqwzsz0mi2w35hb3g2z-insync-1.5.7.37371/client/ fix remove warning.
This is an issue with the packaging. I will try to fix this (should be something easy to do).