Just to let you know, i've built 9.8 from sources found here https://freefilesync.org/download.php.
I'm on Ubuntu 16.04 and wanted a system wide installation of the last version. All binary versions are portable for Linux or outdated .deb.
I've had this error
../Obj/FFS_GCC_Make_Release/ffs/src/ui/main_dlg.o: In function `fff::MainDialog::OnMenuCheckVersionAutomatically(wxCommandEvent&)':
main_dlg.cpp:(.text+0xdc0c): undefined reference to `fff::shouldRunAutomaticUpdateCheck(long)'
../Obj/FFS_GCC_Make_Release/ffs/src/ui/main_dlg.o: In function `fff::MainDialog::OnRegularUpdateCheck(wxIdleEvent&)':
main_dlg.cpp:(.text+0xde59): undefined reference to `fff::shouldRunAutomaticUpdateCheck(long)'
collect2: error: ld returned 1 exit status
make: *** [FreeFileSync] Error 1
BR.