Hello, I try SFTPGo SFTP-server (community edition) to listen to both IPv4 and IPv6. IPv4 is no problem, however I do not manage to use the server with IPv6. 
The ‘network’ related setting of SFTGo under Ubuntu is in config file is: /etc/sftpgo/sftpgo.json
very basic network settings in /etc/netplan/<configfile(s)>.yaml (no issue there).
in the json I tried all kind of settings, nothing successfull.
The probably relevant part of the json is
What ever despite of hours searching the internet, I have no idea how to get this working.
So I hope some one knows how to fix this / can share the solution !