How to scale signed distance field fonts properly?
After some trials I've realized my problem was a programming error and not an actual issue with SDF fonts.
Originally I was rendering the numbers on the texture of the canvas, which had a fixed scale. I thought that it will redraw the quads during the zoom but it wasn't the case. After I've separated the character drawing from the canvas and scaled them separately they finally look sharp.
The linked comments about the small text rendering was slightly misleading. They do have some issues with smaller scale, but that's only the case when the view is zoomed out.