The good news is that it works in release builds, so obviously the bug is in Metal debugger. I was able to bypass the crash by disabling Metal API validation in the app's build scheme.

I can confirm the bug related to SwiftUI table. It crashes somewhere in Metal framework: -[MTLDebugRenderCommandEncoder setRenderPipelineState:]:1616: failed assertion `Set Render Pipeline State Validation For color attachment 0, the texture sample count (1) does not match the renderPipelineState sampleCount (1065353216). 1065353216 is the binary for 1.0 float, so we can guess what the problem is. The bad news is that 15.1 beta 4 (24B5046f) doesn't fix this for my Intel Mac.

The fact that this is documented does not change that this basic functionality is missing. The problem is the forum username is attached to the developer account and you can't just create a new one! Please fix.