Wekan Snap includes full server with database, so Wekan Snap can be installed to local network to server that does not have ports open to Internet. If there is open ports to Internet, Caddy webserver included in wekan provides automatic Let's Encrypt SSL cert, or you can use your own SSL cert, as documented at Wekan GitHub wiki. Also other webservers like Nginx and Apache can be used in front of Wekan to provide SSL.