In Unity 2018.1.0f2 on ArchLinux, there appears to be a bug in the Tile Palette. The Tile Palette always shows blank even though there exist tiles in the palette and I can paint with them.
I’ve attached a screenshot. Even though the tile palette window appears to have no tiles in it, the tiles do exist and I can select and paint with them; however, because the tiles are invisible in the tile palette, it makes using it nearly impossible.