You can find this information in the requirements.txt file - see https://github.com/odoo/odoo/blob/18.0/requirements.txt

For Odoo 18.0 we recommend:
2.0.2 if using Python <= 3.10
2.2.2 if using Python > 3.10 and < 3.12
3.0.1 if using Python >= 3.12