Hi @iRazvan_2745, welcome to the forum 
The new UI has some issues that we are currently working on.
You can track the list of open issues here:
Until we consider the new UI “good enough” the older UI is on.
If you want to try working with the new UI in the local version, you can try out the canary build:
Release: 2.1.0.112 (Canary) 2025-03-26
Just to clarify, the Agent is not 100% self hosted as the UI is hosted on the Duplicati console.
The Duplicati open-source client is 100% self-hostable, and the updated UI will be avaliable for the next stable release.