app/themes/hugo-theme-stack/layouts/404.html

{{ define "main" }}
    <div class="not-found-card">
        <h1 class="article-title">{{ T "notFound.title" }}</h1>
        <h2 class="article-subtitle">{{ T "notFound.subtitle" }}</h2>
    </div>

    {{- $query := first 1 (where .Site.Pages "Layout" "==" "search") -}}
    {{- $searchPage := index $query 0 -}}

    {{- with $searchPage -}}
        <form action="{{ $searchPage.RelPermalink }}" class="search-form widget" {{ with .OutputFormats.Get "json" -}}data-json="{{ .Permalink }}" {{- end }}>
            <p>
                <label>{{ T "search.title" }}</label>
                <input id="searchInput" name="keyword" required placeholder="{{ T `search.placeholder` }}" />
            
                <button title="{{ T `search.title` }}">
                    {{ partial "helper/icon" "search" }}
                </button>
            </p>
        </form>

        <div class="search-result">
            <h3 class="search-result--title section-title"></h3>
            <div class="search-result--list article-list--compact"></div>
        </div>
        
        <script>
            window.searchResultTitleTemplate = "{{ T `search.resultTitle` }}"
        </script>

        {{- $opts := dict "minify" hugo.IsProduction "JSXFactory" "createElement" -}}
        {{- $searchScript := resources.Get "ts/search.tsx" | js.Build $opts -}}
        <script type="text/javascript" src="{{ $searchScript.RelPermalink }}" defer></script>

        <script>
            const wrongUrl = new URL(window.location.href);

            /// Get the search keyword from the wrong URL by removing all slashes and dashes
            const searchKeyword = wrongUrl.pathname.split(/[/|-]/).join(' ').trim();

            document.getElementById('searchInput').setAttribute('value', searchKeyword);
        </script>
    {{- end -}}
    {{ partialCached "footer/footer" . }}
{{ end }}