Not eligible for Winn 11 Upgrade?!

You probably have Windows 11 Home version, other versions will encrypt the drive by default. Windows 11 Home version doesn't include BitLocker


All of my desktops and laptops all run Professional, in fact I don’t think I’ve ever had a device with any version of Windows Home installed.
 
I did some reading, if you setup a Microsoft Account during the setup process then it will encrypt your hard disk and use your online account to store recovery keys should the worst happen.

With my installs I declined using a Microsoft Account and use a local, in that case it won’t as there is nowhere safe to store the recovery keys.