What's the current best device for VR/AR? Have there been any advancements in this field lately? Or any upcoming device that has been announced?
They're all still pretty bad at around 25-40 pixels per degree, with the the higher FoV ones lower PPD.
It varies for each person. Would need to know what you prefer in a device.
Valve's Steam Frame runs Linux that you own, but is not generally available yet if you didn't reserve one already. It suffers from LCD, low pixel density, and awful passthrough, but the software is some of the best and only getting better. In a few years Valve may offer an OLED upgrade (or a new model, but fuck that)
There's a new steam set coming out that looks excellent: https://store.steampowered.com/hardware/steamframe