Low earth orbit is anything below 2000 km. Starlink, the largest constellation by far, operates at or below 570 km. A new batch launched to 340 km was hit by a geomagnetic storm a few months ago, passively coming down within a few weeks. They can also use their ion propulsion systems to come down faster.

Space News article;

"FCC to set five-year deadline for deorbiting LEO satellites'



For the 2022 International Astronautical Congress (IAC 2022), space companies Iridium, OneWeb, and SpaceX (Starlink) have presented a joint paper;

"Satellite Orbital Safety Best Practices"