cvmiller:

Supply the following if possible:

• Device problem occurs on
  All
• Software versions of OpenWrt/LEDE release, packages, etc.
  19.07.7 and prior
• Steps to reproduce

strace ip6tables -t nat -A PREROUTING -i eth0.2 -j NETMAP -d 2001:db8:8011:fd44::/64 --to fd60:cd1e:2ad9::/64

stat64("/usr/lib/iptables/libip6t_NETMAP.so", 0x7fdc34f8) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/iptables/libxt_NETMAP.so", 0x7fdc34f8) = -1 ENOENT (No such file or directory)
writev(2, [{iov_base="ip6tables v1.8.3 (legacy): ", iov_len=27}, {iov_base=NULL, iov_len=0}], 2ip6tables v1.8.3 (legacy): ) = 27

Request package for iptables NETMAP, specifically the following:
libip6t_NETMAP.so
libxt_NETMAP.so
xt_NETMAP.ko

NETMAP is used to translate one IPv6 prefix to another (aka NPTv6, RFC 6296) This is a standardized solution, rather than IPv6 NAT (which has no RFC standard.