Gated-execute on Where ten HTTP header fields are defined

I found the defining section for all ten header fields and read each one on rfc-editor.org. Two RFCs cover eight of them. RFC 9111 (HTTP Caching) defines Age, Cache-Control and Expires. RFC 9110 (HTTP Semantics) defines Last-Modified, ETag, Location, Retry-After and Vary. The other two come from RFC 6797 (Strict-Transport-Security) and RFC 8288 (Link).

Is each RFC still current? My check here is limited. I searched each page for "Obsoleted by", which would appear in the RFC's header if a later RFC had replaced it.

• RFC 9110 matched only in its own section listing the specifications it replaces (https://www.rfc-editor.org/rfc/rfc9110.html).
• RFC 9111 had no match (https://www.rfc-editor.org/rfc/rfc9111.html).
• RFC 6797 matched only an unrelated sentence about other specifications. I searched for the word "Obsolete" there, which is broader, so it would also have caught "Obsoleted by" (https://www.rfc-editor.org/rfc/rfc6797.html).
• RFC 8288's header says "Obsoletes: 5988" and has no "Obsoleted by" line (https://www.rfc-editor.org/rfc/rfc8288.html).

I didn't check the RFC Editor's separate status pages.

Where each field is defined

• Age: RFC 9111 §5.1 (https://www.rfc-editor.org/rfc/rfc9111.html)
• Cache-Control: RFC 9111 §5.2
• Expires: RFC 9111 §5.3
• Last-Modified: RFC 9110 §8.8.2 (https://www.rfc-editor.org/rfc/rfc9110.html)
• ETag: RFC 9110 §8.8.3
• Location: RFC 9110 §10.2.2
• Retry-After: RFC 9110 §10.2.3
• Vary: RFC 9110 §12.5.5
• Strict-Transport-Security: RFC 6797 §6.1, "Strict-Transport-Security HTTP Response Header Field" (https://www.rfc-editor.org/rfc/rfc6797.html)
• Link: RFC 8288 §3, "Link Serialisation in HTTP Headers" (https://www.rfc-editor.org/rfc/rfc8288.html)

The RFC pages wrap lines at a fixed width. Each quote below is one continuous sentence, with the line breaks replaced by single spaces.

{"answers":[
{"field":"Age","rfc":"9111","section":"5.1","quote":"The \"Age\" response header field conveys the sender's estimate of the time since the response was generated or successfully validated at the origin server.","url":"https://www.rfc-editor.org/rfc/rfc9111.html"},
{"field":"Cache-Control","rfc":"9111","section":"5.2","quote":"The \"Cache-Control\" header field is used to list directives for caches along the request/response chain.","url":"https://www.rfc-editor.org/rfc/rfc9111.html"},
{"field":"Expires","rfc":"9111","section":"5.3","quote":"The \"Expires\" response header field gives the date/time after which the response is considered stale.","url":"https://www.rfc-editor.org/rfc/rfc9111.html"},
{"field":"Last-Modified","rfc":"9110","section":"8.8.2","quote":"The \"Last-Modified\" header field in a response provides a timestamp indicating the date and time at which the origin server believes the selected representation was last modified, as determined at the conclusion of handling the request.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"ETag","rfc":"9110","section":"8.8.3","quote":"The \"ETag\" field in a response provides the current entity tag for the selected representation, as determined at the conclusion of handling the request.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"Location","rfc":"9110","section":"10.2.2","quote":"The \"Location\" header field is used in some responses to refer to a specific resource in relation to the response.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"Retry-After","rfc":"9110","section":"10.2.3","quote":"Servers send the \"Retry-After\" header field to indicate how long the user agent ought to wait before making a follow-up request.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"Vary","rfc":"9110","section":"12.5.5","quote":"The \"Vary\" header field in a response describes what parts of a request message, aside from the method and target URI, might have influenced the origin server's process for selecting the content of this response.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"Strict-Transport-Security","rfc":"6797","section":"6.1","quote":"The Strict-Transport-Security HTTP response header field (STS header field) indicates to a UA that it MUST enforce the HSTS Policy in regards to the host emitting the response message containing this header field.","url":"https://www.rfc-editor.org/rfc/rfc6797.html"},
{"field":"Link","rfc":"8288","section":"3","quote":"The Link header field provides a means for serialising one or more links into HTTP headers.","url":"https://www.rfc-editor.org/rfc/rfc8288.html"}
]}