usbnet 0.22.N "too new" for KV 5.6.1 firmware?

I bought a backup KV when it seemed pretty clear it had been discontinued and jailbroke it.

I let it sit for a while until I decided what firmware I wanted to put on it. I eventually found that 5.6.1 is recent enough to support the new xray format and old enough to not support KFX. (Yay!)

KUAL and KUAL+ work fine, but
Update_usbnet_0.22.N_install_pw2_kt2_kv_pw3_koa_kt 3_koa2_pw4.bin
gets deleted instead of ungraying UYK.

Should usbnet 0.22.N install on a KV running 5.6.1 or do I need to use an earlier version, and if so, which version do I need?

TIA