Plan9 (which I actually used for a few years) is caught in the anachronism trap of requiring a three-button mouse to effectively use rio.
It became unbearably obtuse to use on a laptop, and I didn’t like any of the workarounds, so I eventually upgraded my “terminal” to Linux and a custom LXDE setup.
or at least the Acme editor, which is also available for Mac and various Unix systems like Linux, FreeBSD etc.
https://github.com/9fans/plan9port