What do you need the webUI for? What's the use case? Here are a couple for you:
For simple file management and sharing, you may use FileBrowser. It's a single binary written in Go, just download and run.
If you're looking for a more advanced and generic server management solution, then Cockpit is a good option. It's available from Debian's repositories and provides a UI to manage users, storage (including RAID), firewall, system services and even virtual machines. Can also manage Samba shares.
Cockpit uses the same system tooling you would use from the command line. You can switch back and forth between Cockpit and whatever else you like. It wont pollute your system like other solutions and there are dozens of extensions for it.