Original text:
2.1.1. Full-featured hosts are either configured manually with a <del> registration domain, or use the "dr._dns-sd._udp.<domain>" query (RFC6763) to learn the default registration domain from the network. RFC6763 says to discover the registration domain using either ".local" or a network-supplied domain name for <domain>.  Services using SRP MUST use the domain name received through the DHCPv4 Domain Name option (RFC2132), if available, or the Neighbor Discovery DNS Search List option RFC8106.  If the DNS Search List option contains more than one domain name, it MUST NOT be used.  If neither option is available, the Service Registration protocol is not available on the local network. </del>  Manual configuration of the registration domain can be done either by <del> querying the list of available registration zones ("r._dns-sd._udp") and allowing the user to select one from the UI, or by any other means appropriate to the particular use case being addressed.  Full- featured devices construct the names of the SRV, TXT, and PTR records describing their service(s) as subdomains of the chosen service registration domain.  For these names they then discover the zone apex of the closest enclosing DNS zone using SOA queries RFC8765. Having discovered the enclosing DNS zone, they query for the "_dnssd-srp._tcp.<zone>" SRV record to discover the server to which they should send DNS updates.  Hosts that support SRP Updates using TLS use the "_dnssd-srp-tls._tcp.<zone>" SRV record instead. </del>  2.1.2.

Reviewer comments:
The text describing the behavior of full-featured hosts specified behavior that conflicted with the behavior specified in RFC6763 not because a change was needed, but because I just misunderstood how it worked. This change updates that text to simply refer to the relevant section in RFC6763. In addition, the term "zone" was used where "domain" should have been used, and the term "DNS Update" was used to refer to something that should only ever be an SRP update, so these errors are also corrected.

Revised text:
2.1.1. Full-featured hosts are either configured manually with a  <ins> registration domain, or discover the default registration domain as described in RFC6763.  If this process does not produce a default registration zone, the Service Registration protocol is not discoverable on the local network using this mechanism.  Other discovery mechanisms are possible, but are out of scope for this document. </ins> Manual configuration of the registration domain can be done either by  <ins> querying the list of available registration domains ("r._dns-sd._udp") and allowing the user to select one from the UI, or by any other means appropriate to the particular use case being addressed.  Full-featured devices construct the names of the SRV, TXT, and PTR records describing their service(s) as subdomains of the chosen service registration domain.  For these names they then discover the zone apex of the closest enclosing DNS zone using SOA queries RFC8765.  Having discovered the enclosing DNS zone, they query for the "_dnssd-srp._tcp.<zone>" SRV record to discover the server to which they should send SRP updates.  Hosts that support SRP Updates using TLS use the "_dnssd-srp-tls._tcp.<zone>" SRV record instead. </ins> 2.1.2.