Remember, the IPv6 equivalent to RFC1918 IPv4 address is NOT Link Local addresses (FE80::/10).
The closest IPv6 equivalent to what we know as "Private IPv4 addresses" is known as Unique Local Addresses (ULA):
This document defines an IPv6 unicast address format that is globally
unique and is intended for local communications, usually inside of a
site. These addresses are not expected to be routable on the global
ULA Address space exists to address 'internal only' resources, that will never need global route-ability, but might need internal route-ability.
For example, many offices have Printers which operate on a network. There is no reason for the Printer to be accessible (or to be accessing) the Internet, as such, Printers are a good candidate for ULA address space.
There are always exceptions, of course
Or maybe an office has an internal only ticketing system (or CMS, or RMS, or People Portal, or ...) that should only be accessible from the internal, corporate network. If such a tool has no business being accessed from the public Internet, then these might be a perfect candidate for ULA address space.
That being said, Ron is correct, in IPv6 there is no NAT. It was built so NAT could be omitted entirely. And if you properly implement IPv6, you will not be using NAT.
HOWEVER, if there is going to be something NATed in IPv6 (despite best practices), it would be a ULA address to a Global address. It surely won't be link-local address space.
Link-Local addresses (FE80::/10) exists only for local network communication... aka, you communicating with your neighbor, and potentially your router. It is, by definition, not meant to be used to speak to anything on the other side of a router. As such, intrinsincly, you should never come across or try to NAT a Link-Local address to a Global address.
The IPv4 equivlent to the Link-Local address space is the 169.254.0.0/16 range.
This document describes how a host may
automatically configure an interface with an IPv4 address within the
169.254/16 prefix that is valid for communication with other devices
connected to the same physical (or logical) link.