I can recommend https://github.com/frappe/frappe https://github.com/frappe/frappe as a general engine, https://github.com/frappe/erpnext https://github.com/frap

I can recommend https://github.com/frappe/frappe https://github.com/frappe/frappe as a general engine, https://github.com/frappe/erpnext https://github.com/frappe/erpnext is a full blown CRM/ERP built on top of it