I am interested in developing a device compliant with the OpenXR standard. I was able to find the OpenXR API and other information in the reference, but I cannot find the OpenXR Device Plugin Interface. Is this interface publicly available or has it been released yet? In addition, do you have any resources or information that might be useful for this development?
It has not been publicly developed or discussed further. If you are producing a device that includes display, you can make your own runtime, from scratch or based on e.g. Monado or another open source runtime, subject to the license terms. If you are making a peripheral device, you will need to talk to individual runtime vendors. In some cases (e.g. eye trackers or hand trackers), making an API layer can be one method of supporting multiple runtimes, though it requires a lot of maintenance.
The device plugin interface is mainly stalled on lack of folks to drive it forward inside the working group: if it’s important to you, join Khronos and help move it along!