That's great news! That means all .NET EXEs and DLLs will be cross-compatible with Ubuntu since 5.0? Mono had been doing substantial efforts since about a decade but was never the popular choice among Linux devs, mostly due to performance and other issues I think. With Microsoft themselves providing support, things must improve.
As for WinForms, there are probably newer alternatives like MAUI coming up since .NET core.
As for WinForms, there are probably newer alternatives like MAUI coming up since .NET core.