Logged into the End of Time, bought Runes of Shattering from a merchant and adjusted a couple options in loot filter, and traveled to the Reign of Dragons monolith. At this point I didn’t notice if the UI was already missing, I wasn’t really paying attention as I just started my game session. But I opened up the monolith web and traveled to the final story echo/boss fight Emperor of Corpses and it was glaringly obvious I was missing everything on screen.
This was the first time I did the fight, so I first thought the lack of UI was maybe cinematic, but proceeded to start and finish the fight without a hotbar or anything. Loot dropped and I couldn’t highlight/hover over/loot anything. Escape button didn’t pull up any options but I heard a noise like the system thought it was. Hotkeys worked to open up loot filter, inventory, character sheet, etc. Ended up having to close the game with task manager and everything was fixed on restart.
I don’t feel like signing up for an image hosting site to upload the screenshot (you should allow uploads bros), but I had no character portraits in the upper left, no hotbar, no quest guides on the right, no health/mana orbs, no chatbox, nada. I ended the fight and the green “open portal” box opened but that was it.