New bug fix version released.
I have included Python3 Qt5 built for all platforms in this release, also included a few Qt5 related fixes.
The 0.19 conda AppImage theme problem is caused by packing libgtk. I guess libgtk2/3 are on the AppImage/excludedeblist for exactly this reason. Simply delete usr/lib/libgtk* can solve the problem. You may also want to delete usr/lib/libgdk* to get rid of that pixbuf warning as well.