Hi,

You need to move the section and note line checks (line.display_type == 'line_section' and line.display_type == 'line_note') above the product line rendering block.

Please refer to the code below:

<tbody class="invoice_tbody" style="border-bottom:2px solid gainsboro;">
    <t t-set="current_subtotal" t-value="0"/>
    <t t-set="current_subtotal_TTC" t-value="0"/>
    <t t-foreach="o.invoice_line_ids" t-as="line">
        <t t-set="current_subtotal" t-value="current_subtotal + line.price_subtotal"/>
        <t t-set="current_subtotal_TTC" t-value="current_subtotal_TTC + line.price_total"/>
        <tr t-att-class="'bg-200 font-weight-bold o_line_section' if line.display_type == 'line_section' else 'font-italic o_line_note' if line.display_type == 'line_note' else ''">
            <t t-if="line.display_type == 'line_section'">
                <td t-att-colspan="colspan" style="font-weight:bold;">
                    <span t-field="line.name"/>
                </td>
                <t t-set="current_section" t-value="line"/>
                <t t-set="current_subtotal" t-value="0"/>
                <t t-set="current_subtotal_TTC" t-value="0"/>
            </t>
            <t t-if="line.display_type == 'line_note'"
               style="font-size:11.5px !important;font-weight:bold;">
                <td t-att-colspan="colspan" style="font-weight:bold; white-space: pre-wrap;">
                    <span t-esc="line.name"/>
                </td>
            </t>
            <t t-if="line.display_type == 'product'" name="account_invoice_line_accountable">
                <td name="account_invoice_line_name">
                    <span t-field="line.name"/>
                </td>
                <!--                                    <td class="d-none">-->
                <!--                                        <span t-field="line.origin"/>-->
                <!--                                    </td>-->
                <td class="text-end">
                    <span t-field="line.quantity"/>
                    <span t-field="line.product_uom_id" groups="uom.group_uom"/>
                </td>
                <td t-attf-class="text-end {{ 'd-none d-md-table-cell' if report_type == 'html' else '' }}">
                    <span t-field="line.price_unit"
                          t-options='{"widget": "monetary", "display_currency": o.currency_id}'/>
                </td>
                <td t-if="display_discount"
                    t-attf-class="text-end {{ 'd-none d-md-table-cell' if report_type == 'html' else '' }}">
                    <span t-field="line.discount"/>
                </td>
                <td t-attf-class="text-end {{ 'd-none d-md-table-cell' if report_type == 'html' else '' }}">
                    <span t-esc="', '.join(map(lambda x: (x.description or x.name), line.tax_ids))"/>
                </td>
                <td style="border-top-style: hidden;" class="text-end o_price_total">
                    <span t-field="line.price_subtotal"/>
                </td>
                <td style="border-top-style: hidden;" class="text-end o_price_total">
                    <span t-field="line.price_total"/>
                </td>
            </t>
        </tr>
        <t t-if="current_section and (line_last or o.invoice_line_ids[line_index+1].display_type == 'line_section')">
            <tr class="is-subtotal text-end">
                <td></td>
                <td></td>
                <td></td>
                <td>
                    <strong class="mr16">Sous-total</strong>
                </td>
                <td>
                    <span
                            t-esc="current_subtotal"
                            t-options='{"widget": "monetary", "display_currency": o.currency_id}'
                    />
                </td>
                <td>
                    <span
                            t-esc="current_subtotal_TTC"
                            t-options='{"widget": "monetary", "display_currency": o.currency_id}'
                    />
                </td>
            </tr>
        </t>
    </t>
</tbody>

Hope it helps.

I have tried your code but still section is appeared at last, any ways thank you

Maybe try to move the line.display_type == 'line_section' logic before the main <tr> is rendered so that the section row prints before the associated product lines. Like this:

<tbody class="invoice_tbody" style="border-bottom:2px solid gainsboro;">
    <t t-set="current_subtotal" t-value="0"/>
    <t t-set="current_subtotal_TTC" t-value="0"/>
    <t t-foreach="o.invoice_line_ids" t-as="line" t-index="line_index">
        
        <!-- SECTION HEADER FIRST -->
        <t t-if="line.display_type == 'line_section'">
            <tr class="bg-200 font-weight-bold o_line_section">
                <td t-att-colspan="colspan" style="font-weight:bold;">
                    <span t-field="line.name"/>
                </td>
            </tr>
            <t t-set="current_section" t-value="line"/>
            <t t-set="current_subtotal" t-value="0"/>
            <t t-set="current_subtotal_TTC" t-value="0"/>
        </t>

        <!-- NOTE LINE -->
        <t t-if="line.display_type == 'line_note'">
            <tr class="font-italic o_line_note">
                <td t-att-colspan="colspan" style="font-weight:bold; white-space: pre-wrap;">
                    <span t-esc="line.name"/>
                </td>
            </tr>
        </t>

        <!-- PRODUCT LINE -->
        <t t-if="line.display_type == 'product'" name="account_invoice_line_accountable">
            <tr>
                <td name="account_invoice_line_name">
                    <span t-field="line.name"/>
                </td>
                <td class="text-end">
                    <span t-field="line.quantity"/>
                    <span t-field="line.product_uom_id" groups="uom.group_uom"/>
                </td>
                <td t-attf-class="text-end {{ 'd-none d-md-table-cell' if report_type == 'html' else '' }}">
                    <span t-field="line.price_unit" t-options='{"widget": "monetary", "display_currency": o.currency_id}'/>
                </td>
                <td t-if="display_discount"
                    t-attf-class="text-end {{ 'd-none d-md-table-cell' if report_type == 'html' else '' }}">
                    <span t-field="line.discount"/>
                </td>
                <td t-attf-class="text-end {{ 'd-none d-md-table-cell' if report_type == 'html' else '' }}">
                    <span t-esc="', '.join(map(lambda x: (x.description or x.name), line.tax_ids))"/>
                </td>
                <td class="text-end o_price_total" style="border-top-style: hidden;">
                    <span t-field="line.price_subtotal"/>
                </td>
                <td class="text-end o_price_total" style="border-top-style: hidden;">
                    <span t-field="line.price_total"/>
                </td>
            </tr>
            <!-- Update subtotals -->
            <t t-set="current_subtotal" t-value="current_subtotal + line.price_subtotal"/>
            <t t-set="current_subtotal_TTC" t-value="current_subtotal_TTC + line.price_total"/>
        </t>

        <!-- SUBTOTAL AFTER LAST LINE IN SECTION -->
        <t t-if="current_section and (line_index + 1 == len(o.invoice_line_ids) or o.invoice_line_ids[line_index + 1].display_type == 'line_section')">
            <tr class="is-subtotal text-end">
                <td></td><td></td><td></td>
                <td><strong class="mr16">Sous-total</strong></td>
                <td>
                    <span t-esc="current_subtotal"
                          t-options='{"widget": "monetary", "display_currency": o.currency_id}'/>
                </td>
                <td>
                    <span t-esc="current_subtotal_TTC"
                          t-options='{"widget": "monetary", "display_currency": o.currency_id}'/>
                </td>
            </tr>
        </t>

    </t>
</tbody>