There if FriendSky mobile app for iOS and Android. FriendSky is in beta VIP testing. It is also possible to install Friend server from source code and use same iOS and Android apps with it https://github.com/wekan/wekan/wiki/Friend . Inside Friend is desktop, where Wekan app icon can be installed. There will later be Wekan integrations to Friend drives like Google Drive/Dropbox/sftp/Samba/Weddav . Anyway, inside Friend there is Wekan webbrowser version in window. But if you don't need all the functionality of Friend, you can just run Wekan in mobile Chrome webbrowser. There is in progress fixes to improve mobile web usability, a lot is already added.
Also, as Stefan said above, current trend is also to make PWA apps. For that, Wekan already has manifest file, that I have tested with desktop chrome app mode that it works, launching Wekan like app, without browser menus. Most likely it's also possible somehow to add Wekan as app icon to Android and iOS like any other PWA app, but if it's still missing some related functionality, it could be added later.
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.