Could someone please try installing this? I'd be really curious to see what Windows 7 on a Steam Deck would look like!

breathlessly storms out the door with pitchfork in hand

chaaaaaarge!

You don't need a Steam Deck for this, it can be installed on regular Linux distributions on PC. On Steam Deck it would exactly the same. Look at the screenshots on the link you gave. This is how it will look like on Steam Deck.

Edit: However I do not recommend to install this project on a Steam Deck, because it changes files that is not meant to be changed. And on Steam Deck with its write lock this can cause problems:

DISCLAIMER:

This project modifies a small number of KDE Plasma UI components which are not meant to be modified. Make sure to create backups before attempting to install this project. I am not responsible for broken KDE and/or Linux installs.

Because this project is under development and relies on upstream for a lot of things, many things are subject to change and will likely break as KDE Plasma gets updated over time. Keep an eye out on the issue tracker for further details when things inevitably happen to break.

Lastly, feel free to fork this project and/or contribute to it in any way. Any and all effort is greatly appreciated.