Hi,

Here is custom module please try this,

__manifest__.py
{

    'name': 'Readonly Timesheet Grid',

    'version': '1.0',

    'summary': 'Make timesheet hours readonly in Grid View',

    'category': 'Human Resources',

    'depends': ['hr_timesheet'],

    'data': [

        'views/timesheet_grid_view.xml',

    ],

    'installable': True,

    'application': False,

    'auto_install': False,

}

views/timesheet_grid_view.xml – Override Grid View

<odoo>

    <record id="readonly_timesheet_grid_view" model="ir.ui.view">

        <field name="name">account.analytic.line.grid.readonly</field>

        <field name="model">account.analytic.line</field>

        <field name="arch" type="xml">

            <grid string="Timesheets (Readonly)" cell_edit="false">

                <field name="employee_id" type="row"/>

                <field name="project_id" type="row"/>

                <field name="task_id" type="row"/>

                <field name="date" type="col"/>

                <field name="unit_amount" readonly="1"/>

            </grid>

        </field>

    </record>

</odoo>

I hope it is usefull

please did you find any solution? i am facing the same problem