Creating the share via /etc/samba/smb.conf does work but that is not user friendly. Unfortunately the nautilus-share extension for Nautilus/Files is currently broken. No idea if I broke it with the recent samba stack update or it has been broken for a long time and gone unreported.
I have pushed a fix to the unstable repository so it may land next sync. I say may because as has already been mentioned upstream (makers of the extension) have deprecated / archived the project so Solus may decide to deprecate it from the repo as well. But for now it remains.
