- Qubes-Whonix ™ users should consider creating a separate, cloned
whonix-ws-16-onionshareTemplate before installing OnionShare/flatpak.
- OnionShare from the Debian stable repository is suitable for most users. Flatpak can be utilized for later OnionShare versions; v2.4 is packaged at the time of writing. 
onionshare via flatpak.
To see what's happening "under the hood".
0.0.0.0, meaning listening on all interfaces which is required in case of Whonix ™ so onionshare running inside Whonix-Workstation ™ can be reached from Whonix-Gateway ™. (As opposed to onionshare running on a host without Whonix ™ where it should listen on localhost
Proto Recv-Q Send-Q Local Address Foreign Address State User Inode PID/Program name [...] tcp 0 0 0.0.0.0:17605 0.0.0.0:* LISTEN 1000 30959 4009/python3