16-bit printing with Lightroom Classic on Windows10

"my prints from Lightroom look as if they were 8bit only"

The only theoretical advantage of higher bit depth is to eliminate banding and posterization. That's critical in some stages of the process, like editing and display, less so at the print stage. Do you see banding?

That said, it's 2020 and in principle, there's no particular reason we should have to settle for 8 bit processing anywhere.

As far as I know, no Windows print drivers support 16-bit printing, but some print drivers for Mac do.

According to this thread on DPreview, there is no difference whatsoever between an 8-bit and a 16-bit print.

I'm guessing that the reason is that printers are not able to distinguish the  65,536 levels per channel.

You can't distinguish them on screen either, but they provide editing headroom, which is the purpose of 16-bit.

So if you're not happy with your prints, it's not because they're printed from 8-bit files, there has to be some other reason.

16-bit printing is Mac only.

You might also find this page from Help is a useful resource https://helpx.adobe.com/lightroom-classic/help/print-job-options-settings.html