Split
You can usually spot a split keyboard if it has two seperate PCBs connected by a cable. Split keyboards literally half the keyboard to better the ergonomics and encourage better touch typing. The ones mentioned here are only a few.
Kinesis Advantage2
The Kinesis Advantage 2 is a an ergonomic keyboard with Cherry MX Brown switches, 20 degrees of tenting, integrated palm supports, and more.
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ErgoDox
The ErgoDox is a keyboard built for complete ergonomics that splits the keyboard in half, allowing you to open your chest and widen your arm span while you are typing. Their online store allows you to highly customize your ErgoDox so that it's ready to go when it reaches your doorstep. Their new offering, the Moonlander, allows you to customize different angles on the keyboard, fold into to a carrying package and much more.
View on ErgoDoxQMK FirmwareMontsinger Rebound
The Rebound is a 50% split ortholinear keyboard and is made to fit into most 60% percent keyboard cases. It is highly customizable with space in the middle of the keyboard for additional switches and support for a rotary encoder. The keyboard isn't available pre-built and the parts must be purchased seperately.
Buy the Rebound