Agree with the parent that there is no need for a ULA registry for locally assigned addresses under RFC 4193 (which is every one I've ever seen). But there is that option for globally assigning addresses that I'd be intrigued to see if anyone does anything with...
Also important to note that while RFC1918 is roughly equal to RFC4193/ULA, that "site local" is another beast entirely (FECO ) that was, as you noted, ambiguous and was deprecated in rfc3879
Also important to note that while RFC1918 is roughly equal to RFC4193/ULA, that "site local" is another beast entirely (FECO ) that was, as you noted, ambiguous and was deprecated in rfc3879