Built and published a small .NET Core app under Ubuntu that was running on the Windows Subsystem for Linux. Executable ran flawlessly on a RHEL 7 machine that didn't have .NET installed at all. I guess the self-contained and trimmed project builds work. The win-x64 target ran on a XP VM.
Not too shabby. Too bad the cross-platform GUI stuff won't happen until MAUI is done (sometime around .NET6). .NET 5.0 will be released tomorrow so that'll be another year at least.