According to http://repo.tinycorelinux.net/16.x/aarch64/tcz/src/neatvnc/compile_neatvnc, it's compiled with ffmpeg7.
However, its dependencies list libavfilter.tcz instead of libavfilter7.tcz.
And yet "ldd usr/local/lib/libneatvnc.so.1.0.0" indicates that it is actually compiled against /usr/local/lib/libavfilter.so.7 (libavfilter.tcz/ffmpeg.tcz).
That is, it seems that compile_netvnc is wrong.