If it's obvious to anyone with a telescope, that at least Jupiter is a sphere, why would Earth be flat?
One answer I hear from flat earthers is that other planets are round, but not Earth.
The other answer is that space is some sort of projection, and you're not seeing planets are all.
Look into project bluebeam for the projection. I seriously doubt the ISS can be spotted on any clear night.
When we have the technology to do projections ?