xsl:template match doesn't match the specific xml tag as expected

Question

I have the following docbook xml file in version 5.

<?xml version="1.0" encoding="UTF-8"?>
<book version="5.0" xmlns="http://docbook.org/ns/docbook" xmlns:xi="http://www.w3.org/2001/XInclude">
    <info>
        <title>Title1</title>
        <cover>
            <para>
                <para>a paragraph</para>
            </para>
        </cover>
    </info>
    <!-- Part A -->
    <part>
        <title>Part A</title>
        <chapter label="1">
            <title role="HEAD-1">Chapter1 from PartA</title>
            <para role="richtext">
                <para role="richtext"> Text in paragraph </para>
            </para>
        </chapter>
        <chapter label="2">
            <title role="HEAD-1">Chapter2 from partA</title>
            <para>Another paragraph</para>
        </chapter>
    </part>
    <!-- Part B -->
    <part>
        <title>Part B</title>
        <chapter label="1">
            <title role="HEAD-1">Chapter1 from PartB</title>
            <section>
                <title role="HEAD-2">Section1 from Chapter1 of PartB</title>
                <para>a paragraph <ulink url="http://alink2">a link2</ulink></para>
            </section>
            <section>
                <title role="HEAD-2">Section2 from Chapter1 of PartB</title>
                <para>a paragraph <ulink url="http://alink2">a link2</ulink></para>
            </section>
        </chapter>
    </part>
</book>

I'm trying to convert it to html through xslt v3 and by modifying specific elements ( I have used the saxon xslt library for java) such as the title and the ulink, i.e.

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet
        xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
        xmlns:xs="http://www.w3.org/2001/XMLSchema"
        xmlns:db="http://docbook.org/ns/docbook"
        xmlns:m="http://docbook.org/ns/docbook/modes"
        xmlns:h="http://www.w3.org/1999/xhtml"
        xmlns="http://www.w3.org/1999/xhtml" exclude-result-prefixes="xsl xs db m h"
        version="3.0">

    <xsl:import href="https://cdn.docbook.org/release/xsltng/current/xslt/docbook.xsl" />

    <xsl:template match="db:ulink" mode="m:docbook">
        <xsl:variable name="url" select="@url"/>
        <xsl:variable name="name" select="normalize-space(.)"/>
        <a href="{$url}" title="{$name}">
            <xsl:value-of select="$name" />
        </a>
    </xsl:template>

    <xsl:template match="db:title" mode="m:docbook">
        <xsl:variable name="header" select="@role"/>-->
        <xsl:variable name="title" select="normalize-space(.)"/>

        print something e.g. <xsl:value-of select="$title" />
    </xsl:template>
    
</xsl:stylesheet>

The ulink works as expected however I can't get the title correctly. I have tried different paths but with no success. A similar question was here xsl:value-of not working but it didn't help in this case.

The output I get is

<nav xmlns="http://www.w3.org/1999/xhtml" class="top"></nav><main xmlns="http://www.w3.org/1999/xhtml">
   <article class="book">
      <header>
         <h1>Title1</h1>
      </header>
      <article class="part">
         <h1 class="title">Part A</h1>
         <article id="R_part1" class="part">
            <header>
               <h1><span class="label">Part<span class="sep">&nbsp;</span></span><span class="number">I<span class="sep">. </span></span>Part A</h1>
            </header>
            <div id="R_part1_ch1" class="chapter" db-label="1">
               <header>
                  <h1><span class="label">Chapter<span class="sep">&nbsp;</span></span><span class="number">1<span class="sep">. </span></span>Chapter1 from PartA</h1>
               </header>
               <p class="richtext">
                  
                  <p class="richtext"> Text in paragraph </p>
                  </p>
            </div>
            <div id="R_part1_ch2" class="chapter" db-label="2">
               <header>
                  <h1><span class="label">Chapter<span class="sep">&nbsp;</span></span><span class="number">2<span class="sep">. </span></span>Chapter2 from partA</h1>
               </header>
               <p>Another paragraph</p>
            </div>
         </article>
      </article>
      <article class="part">
         <h1 class="title">Part B</h1>
         <article id="R_part2" class="part">
            <header>
               <h1><span class="label">Part<span class="sep">&nbsp;</span></span><span class="number">II<span class="sep">. </span></span>Part B</h1>
            </header>
            <div id="R_part2_ch1" class="chapter" db-label="1">
               <header>
                  <h1><span class="label">Chapter<span class="sep">&nbsp;</span></span><span class="number">1<span class="sep">. </span></span>Chapter1 from PartB</h1>
               </header>
               <section id="R_part2_ch1_s1" class="section">
                  <header>
                     <h2><span class="number">1<span class="sep">&nbsp;</span></span>Section1 from Chapter1 of PartB</h2>
                  </header>
                  <p>a paragraph <a href="http://alink2" title="a link2">a link2</a></p>
               </section>
               <section id="R_part2_ch1_s2" class="section">
                  <header>
                     <h2><span class="number">2<span class="sep">&nbsp;</span></span>Section2 from Chapter1 of PartB</h2>
                  </header>
                  <p>a paragraph <a href="http://alink2" title="a link2">a link2</a></p>
               </section>
            </div>
         </article>
      </article>
   </article>
</main><nav xmlns="http://www.w3.org/1999/xhtml" class="bottom"></nav>

Any ideas?