At Ignite 2021, Microsoft today announced Microsoft Mesh, an Azure-based cloud platform that will allow anyone to build immersive, multiuser, cross-platform mixed reality apps. Mesh can be used to improve virtual meetings, conduct virtual design sessions, assist remotely better, host virtual social gatherings and more.
As you can see from the above image, Microsoft Mesh supports various platforms including Microsoft HoloLens, Windows Virtual Reality headsets, Oculus Quest 2, phones and tablets on iOS or Android and PCs and Mac for 2-dimensional viewpoint.
The new Microsoft Mesh app for HoloLens is one of the first apps built on Microsoft Mesh platform, you can read about it here.
You can find technical details about the Microsoft Mesh platform here.