A bunch of VR headsets (including fairly expensive ones) used Windows Mixed Reality as their API to the OS. Without it, many of these headsets simply do not function. Turning your very expensive purchase into a paperweight.

Microsoft got companies like Samsung, HP and Lenovo to make WMR VR headsets that require the WMR Windows components. There is official support for Steam VR, but the headsets don't work if the WMR components aren't there, and after November there will be no officially supported version of Windows with those components. From what I've read it's basically impossible to get WMR working on 10 LTSC, and I assume the situation is the same on 11 LTSC.