I cannot select 5.7.0. I don't think this is a killer, but I previously compiled a few projects with that OS and I would have to update a bunch of devices.
Anyone know why?
We do not recommend using Device OS 5.7.0 due to bugs in that release.
For M-SoM, P2, and Photon 2, the best option is 5.6.0. There will be a 5.8.2 in the future.
For all other devices, 6.1.0, 5.8.0, or 5.6.0 are all fine.