There's actually a good primary source for this cited in the article [0], stating: "However, at low elevations near twilight at intermediate latitudes (45°–55°

There's actually a good primary source for this cited in the article [0], stating: "However, at low elevations near twilight at intermediate latitudes (45°–55°, e.g., much of Europe) hundreds of satellites may be visible at once to naked-eye observers at dark sites." This is referring to Starlink's 12000 satellite constellation, so thousands absolutely is the order of magnitude we're talking about when (if) they go to the planned 30000 and when other companies do the same. [0] https://iopscience.iop.org/article/10.3847/2041-8213/ab8016 https://iopscience.iop.org/article/10.3847/2041-8213/ab8016