I'm a long time MS Natural 4000 user. That said, I think the X-Bows Knight keyboard looks interesting. Thumb keys for enter, ctrl and shift. Still has function keys which a lot of these other keyboards don't (and some of us still use). https://x-bows.com/products/x-bows-knight-ergonomic-mechanic...
I've also gotten very use to the media and additional silver buttons along the top of the MS Natural 4000, which I've set as short-cuts for various things. I almost need a separate little keypad that I can program before I give up the 4000.
1: https://github.com/qmk/qmk_firmware/tree/master/keyboards/xb...