It depends on the quality and performance requirements, but you are basically on your own (e.g. the browser's integrated text rendering won't be of much help unfortunately - at least if performance matters). You need to bring your own font data and 'pre-rasterize' glyphs either on the CPU or GPU into a font cache texture, or render directly on the GPU using an approach like Slug or Pathfinder.

Of course there's also always the option to overlay DOM elements over the WebGPU canvas if you just want to render some 2D UI on top of the 3D rendering.