I had a Mantis Q40 Braille display/keyboard combo for testing last year. I used it for about six weeks before I had to send it back. Couldn't afford to buy it at the time. I have since used other displays I own, with varying keyboards as combinations. But I must say, none parallels the integrated experience of the Mantis. Sadly, HumanWare currently don't list any dealers in Germany who carry their Braille products. Which surprises me. But their dealer locator only shows Low Vision products, not Braille. That's a bit disconcerting, since I'd require a German language version. Well, will need to investigate some more.
That reminds me, do HumanWare have a presence in the #Fediverse yet?