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.
I've asked this question before to FE folks and they had responded that the firmament contains a projection of such images.
More evidence disputing FE is satellites and, in particular, their data. There's PBs of data / day in remote sensing available. Would be quite difficult to fabricate such and even if they did I suspect we'd notice.
Who or what do they say does the projection? If you're using a literal, and very awkward, Bible interpretation I suppose that is one answer.
Please don't confuse my ability to understand a point of view with my support for the same. If you don't understand something, you really cannot question it appropriately.
How does one understand something without questioning it?
If your goal is to understand it, the questions will be illuminating. If your goal is to dismiss it, your questions will be cursory