NuttX has support to USB Mouse and keyboard, whoever only few USB Keyboards will work. I know a keyboard that some users reported to work correctly is the Perixx PERIBOARD-409U Wired USB Mini Keyboard.
I decided to test a generic mini keyboard from China, but it is not working. Most of the time the /dev/kbda is not created and when it is created it is not working:
ABCDF nsh> ls /dev /dev: console kbda null ttyS0 nsh> ? help usage: help [-v]  NuttShell (NSH) NuttX-10.0.1 nsh> OTGFS ERROR: ctrl_senddata() failed with: 11 . cat dd false ls ps sleep uname [ cd df free mkdir pwd source umount ? cp echo help mkrd rm test unset basename cmp exec hexdump mount rmdir time usleep break dirname exit kill mv set true xd Builtin Apps: sh nsh hidkbd nsh> hidkbd Opening device /dev/kbda Device /dev/kbda opened
If you get some other keyboard working, please comment here!