Does Debian require packages to work on all of its architectures? If so, that could be the issue. .NET Core only supports x86, x64, and Arm64 (I think Arm32 has been discontinued and RISC-V is experimental at this point).
It's possible that they object to .NET Core having certain license restrictions on the Windows port (https://github.com/dotnet/core/blob/main/license-information...). .NET Core is mostly MIT or Apache licensed, but the Windows SDK has some additional terms. Skimming the third party licenses, that doesn't seem like an issue (mostly MIT/BSD/Apache or similar).
I think the licensing situation is an interesting question: if you have software that's 100% open source when compiled for your OS, but requires non-free stuff to run on Windows, is it ok to include in Debian? It looks like none of the non-free stuff (like WPF) gets distributed with the non-Windows SDK builds. Binaries created from your code only depend on MIT-licensed stuff on macOS and Linux, but might depend on something closed-source when targeting Windows - though it looks like almost all of that stuff is either WPF (so you wouldn't be able to develop on Linux/Mac anyway since those libraries wouldn't be in the SDK on those platforms) or were removed as a runtime dependency in .NET 7. It looks like `Microsoft.DiaSymReader.Native` might be the only thing left. Maybe that's what is holding it back?
> also, does dotnet-core have a reasonable aot story for things like esp32 and ch32v003?
"Reasonable" can be a lot of things to a lot of different people. People have been working on RISC-V support. Samsung seems interested in it. But I probably wouldn't recommend it at the moment - and Mono doesn't really have RISC-V support either.