It’s just a floating panel which is relatively new to KDE Plasma. The Plasma theme is Arch Round.

Details:
Global theme: Catppuccin Mocha
Icon theme: Tela circle

I’m glad Ars seems to have walked back its transphobia after the absolute shit-show that was its article about twitter screening a self identified fascist’s transphobic screed that somehow came down on the side of the fascist.

It’s also in testing on Android