Some Guides for hardening IPv6:
Windows: https://www.ernw.de/download/ERNW_Guide_to_Configure_Securely_Windows_Servers_For_IPv6_v1_0.pdf
Linux: https://www.ernw.de/download/ERNW_Guide_to_Securely_Configure_Linux_Servers_For_IPv6_v1_0.pdf
Mac: https://www.ernw.de/download/ERNW_Hardening_IPv6_MacOS-X_v1_0.pdf