What is the current best practice for developing / submitting to the Windows 10 store? Has anyone submitted an OpenFL app to the Windows 10 store?
The last I tried to submit to the Windows store (Then Windows 8) was about a year ago with Lightbot and at that point the only simple(-ish) option was to export to HTML5 and then wrap it in a basic webframe in Visual Studio before submitting. Is there a better way today?
Yes, currently you can go to the Windows Store using HTML5 + a manual wrapper. We use WebGL by default now on HTML5, so this might perform better than it did in the past, unless there are problems with how embedded web content works.
We have no official support for Windows Universal Apps, however, there are a couple strides that may bring this nearer to reality. We have support for ANGLE integrated, and have budding support for C#. ANGLE (particularly) should help, since Windows Universal Apps do not have OpenGL access as far as I know