Yup. It's true.

Server2019
When can I use it?

We're not planning on extending support to Server 2019, because there are certain OS features we depend upon that are only available on Windows 18362 and above.

This is sad.
You know the main target audience for Windows Terminal, right? It is very frustrating that for some unclear reason I cannot use the application for managing my servers as they don't (and will not to in observable future) be updated to latest 18362. This is kind of things that remind you that despite its cool and stuff its still Microsoft.

for some unclear reason

there are certain OS features we depend upon that are only available on Windows 18362 and above

That seems like a pretty clear reason to me. Namely, the features that are missing are "XAML Islands" and unpackaged/side-by-side winrt activation. The Terminal can't really draw any UI without xaml islands, and we' can't do very much of anything without the second.

Thank you @zadjii-msft for quick and honest answer. I appreciate the intentions of the developers making Terminal and apologize if my previous comment is offensive in any kind.
However, if we take a look more deeply, on higher level, the root of the problem persists in my opinion.

1. According to ms blog https://blogs.windows.com/windowsdeveloper/2018/11/02/xaml-islands-a-deep-dive-part-1/ the XAML Islands was announced back in 2018, included only in 2019 may update 18362

2. There was intention decision to 100% rely on this technology back in July 2019 - first Terminal release - month or so after XAML Islands its just released officially.

Conclusion: As an engineer I understand the urge to try latest and greatest things.
But, hey, the target audience of Terminal is not accountants or - its IT enthusiasts, professionals, system administrators.
The urge of having better tooling for windows, including cmd among this people is big.
So in this case intention decision to ignore all of these users - the Win 7 (still 30% of market as of today), Win 8, Win Server 2016, Win Server 2019 even.... It's just...sad, you know?

Even its completely logical and valid, the fact that one need to update entire OS just to finally have cool terminal in windows is killing me.

Again, I appreciate the work, the app is free and I have no right to complain about it, so please ignore.

Thanks for the reminder to lock this thread.