The team of Synfig told us about the latest candidate:
For those who impatient about the upcoming release, we providing a testing linux binaries with the most features inside!
Please check out this forum thread, install and test.
Note: Yes, the version in package number still says 0.63.05, but it doesn't really matter, believe us.
I got this error with my old fedora distro:
synfigstudio: symbol lookup error: /opt/synfig/lib/libcairo.so.2: undefined symbol: pixman_image_composite32