You need to override the method that parses the duration input to handle both commas and points as decimal separators.

from odoo import models, fields, api
from odoo.exceptions import ValidationError
import re

class TimesheetCustom(models.Model):
    _inherit = 'account.analytic.line'

    @api.constrains('unit_amount')
    def _check_unit_amount(self):
        for record in self:
            # Replace comma with dot for decimal values
            if isinstance(record.unit_amount, str):
                record.unit_amount = record.unit_amount.replace(',', '.')
            
            # Validate the converted value
            try:
                float(record.unit_amount)
            except ValueError:
                raise ValidationError("Please enter a valid duration.")

Ensure the views are updated to handle the input correctly. You have to override the  field "unit_amount" and add float_time widget to it.

Hello,

Nobody can help me.

Is someone from the odoo Core can answer or create a bug ticket ?

Regards