The Compose Preview tool has been flaky for years. It would crash, refuse to render custom fonts, or just show a blank gray box.
You literally click "Device Streaming," pick a phone from a list of real hardware in Google's data centers, and it streams to your IDE like you're plugged in via USB. android studio koala download
So, clear some disk space (it’s still a 1.5GB download, sorry), back up your /.android folder, and take Koala for a spin. The Compose Preview tool has been flaky for years