expire? That's sure for Evaluation and Insider Preview (except which use official release activation, like 19042, and 17784.1608 AzureStackHCI.).
No. (Before End of Service) It will receive updates but install failed (except Windows Defender and .NET48 RollupFix).
I would love to make some program which adds GUI to Server Core, but I simply don't have skills to that. Also it could be more friendly to beginners for Windows Server Core.
what editions get updates? i don't know which I should use. starter-based ltsc looks nice but if it doesn't get updates I don't want to get hacked.