https://github.com/gnu-octave/octave/commit/e21b1898cb6507dff38679c25b4db7fde44de883
From e21b1898cb6507dff38679c25b4db7fde44de883 Mon Sep 17 00:00:00 2001
From: "Dmitri A. Sergatskov" <dasergatskov@gmail.com>
Date: Sun, 8 Mar 2026 16:08:04 -0400
Subject: [PATCH] Fix Qt help generator for Texinfo 7.3 Function-Index output.

Texinfo 7.3 changed the HTML classes used for the function index.
Update the Qt help generator to handle both the old and the new HTML
forms when parsing Function-Index.html.

* mk-qthelp.pl: Accept new printindex-style function
index table classes in Function-Index.html parsing.

diff --git a/doc/interpreter/mk-qthelp.pl b/doc/interpreter/mk-qthelp.pl
index 475ba20b22..a68af8b0ad 100755
--- a/doc/interpreter/mk-qthelp.pl
+++ b/doc/interpreter/mk-qthelp.pl
@@ -72,7 +72,12 @@ open ($HTML, "<", $htmlfname) or die "Unable to open $htmlfname";
 
 # Skip through preamble of file to find start of list
 while (defined ($_ = <$HTML>)
-         and ! /^<table class="(?:index-fn|fn-entries)/ ) {;}
+         and ! /<table\b[^>]*\bclass="[^"]*\b
+                 (?:
+                   index-fn |
+                   fn-entries |
+                   fn-entries-printindex
+                 )\b/x ) {;}
 
 die "Function-Index.html: reached EOF without finding data start pattern"
   if eof ($HTML);
-- 
2.49.1