An insider build of the Groove Music UWP app (Version 10.17083.18151.0) which features a scrapped visualizer that did not make it into stable builds. This was featured as only a few screenshots on online articles (not explaining how to get it), and then was kinda lost.
The visualizers are called "Dots" and "Ribbons", you can choose to change visualizer every song or settle on one of these.
"Ribbons" visualizers change their color scheme after a while. The first visualizer under "Dots" takes the cover art of the album/single or a generic Groove logo if the audio file lacks a cover art.
In order for this build to work properly (otherwise it takes forever before playing a song and doesn't see your music library folders if installed with another package name which you can edit in the AppxManifest file) you need to replace Groove Music on Windows 10 or 11, or Media Player on Windows 11 with this version. Just right click it in the start menu and uninstall the current version, then double click the appxbundle file and install this Groove build (no developer mode enabled is needed).
To get the latest version of the Groove/Media Player app just update it through Microsoft Store and the latest app should reinstall again.
Getting the visualizer, and equalizer to work
Download the settings.dat file, and put it in %localappdata%Packages\Microsoft.ZuneMusic_8wekyb3d8bbwe\Settings\
You should then see the visualizer by clicking the bottom left corner when a song is playing (where the song cover art, title and artist is) and then you should see a button above in the screen. If you don't, your system may not be compatible or your GPU drivers aren't up to date.
This visualizer uses heavy shaders, composition effects and Direct2D so GPU support isn't granted.
I've had the most luck with Intel iGPUs, tested HD 620 (i3-7020u), HD 520 (i5-6300u) and "Intel HD Graphics" from 2016 (Celeron N3450). Also tested "Intel HD Graphics" from 2012 (Celeron B830) but the visualizer didn't work which is expected due to the age of that iGPU.
AMD GPUs apparently don't work well with some Composition effects so your mileage may vary, the Radeon Graphics on my Ryzen 3 3250u for example don't work with this visualizer, despite being newer than all the above.
Here's a video of the visualizer in action (very laggy and just.. bad but still leaving it up since no one else made any other video yet): https://youtu.be/8qAEpH2qLC4
Another one i've made which shows some more "Ribbons" color combinations: https://www.youtube.com/watch?v=rK5pgzz3IbE