It seems that Microsoft has decided to modernise their UI Icons to make them rounder, and more friendly.

https://medium.com/microsoft-design/developing-an-open-source-icon-system-at-microsoft-b1796315df9f

• So will these replace the MDL2 ones with WinUI 3?
• Will they still come as a font?
• Will there be a version on a 16px grid so as to act as a 1:1 replacement for MDL2 Icons?
• Will the 24px versions also be included as a font choice, and which controls would move to use them? (I could see these working well for Icon Buttons and ApplicationBar Buttons)

https://www.figma.com/community/file/836835755999342788/Microsoft-Fluent-System-Icons
24px grid Icons released to the community through Figma