I've tested a few versions.
4.3.8 On ore appears to be the last working version

4.3.75 Also on ore is where the breakage begins.

I also tested the latest and oldest available versions on Jenkins (that I could manage to find)
4.4.4 and 4.3.108 and neither of those worked.

Tested with
Nucleus: 1.9.2-S7.1
Sponge: 7.1.6-RC3616

Steps to reproduce:

/lp creategroup mod
/nucleus setupperms mod mod

/lp group mod permission list -> just for listing perms, also doesn't show up in editor either.

Thanks for reporting - sorry it took a while for me to get around to fixing it! :)