Recently I happened to be reading up on Ubuntu and noticed a few interesting additions to their desktop environment offerings.
This isn't yet an official "flavour", but I thought it was interesting enough to take a look at anyway.

The Sway desktop enviroment is a tiling window manager, effectively the same as i3 but designed for Wayland instead of XOrg. In practice it can be a confusing desktop environment as a lot of the window controls are implemented using the keyboard instead of the mouse as is traditional.
These screenshots are of the latest release (24.04). I had a lot of problems with this version of Ubuntu; the system requirements are quite high, particularly on the GPU side of things. Even with the suggested VirtualBox profile the desktop would just crash out to a login prompt every time I tried loading it. VMWare worked, but it was still extremely slow at times, and several applications (notably LibreOffice and the installer) both crashed the desktop every time I tried running them. As such these screenshots are from the live CD.

The default desktop, with the welcome screen open.

As you can see, there are no visible window controls. The expectation is that you will do most of your window management through the keyboard; in fact the whole desktop could be operated without a mouse (but mouse controls are still present).
Also, since this is a tiling window manager, generally you can't have overlapping windows, similar to very early Windows. Sway does make a concession that the previous i3 doesn't and allows for at least some windows to be floated like a traditional desktop, though.

Clicking on the rocket ship icon (I guess another way of saying "Launchpad" without blatantly copying Apple) shows a list of installed applications. As with other distros there is a half-hearted concession here towards having hierarchies, but it defaults to a pointlessly long "all" view. Although I guess when it takes up the entire screen it's not that long anymore.

Here is Firefox, standard browser, but as is tradition it doesn't quite conform to the window manager standard as there is a visible close button.

Here is the file manager, which you will notice has started full-screen. This is also a fairly standard file manager layout with the usual suspect views and such things.

I also noticed quite quickly that the file manager had no real way to navigate folders visible by default, which was quite odd.
Seems the expectation is to use keyboard shortcuts like the rest of the desktop. This is starting to feel like my old MS-DOS experiences, memorizing hundreds of keyboard shortcuts to do basically everything.