Apple removed the app from the store as it was an outdated ionic v1 app which Apple doesn’t allow anymore.
I haven’t had the time to rewrite the iOS app from scratch with something like react-native.
Every install of the open-source version should have a mobile view that would allow you to use the instance on a phone. (only downside is that push notifications would not exist)
I am in the process of decommissioning the old TPS Server as the app is no longer available.