Customer Relationship Management

Customer Relationship Management (CRM) allow you to manage customers.

HubSpot

Fre plan allow unlimited users, unlimited contacts, shared inbox and ticket system. Look like a good system to use as shared inbox/helpdesk. They have google chrome extension, that integrate with gmail/google workspace so all emails get tracked in CRM with read notifications.

https://hubspot.com/

Agile CRM

Free for upto 10 users. Helpdesk.

https://www.agilecrm.com

Bitrix24

Bitrix24 is Open source CRM. Paid and Free Options available.

https://www.bitrix24.com/uses/free-open-source-crm-software.php

See ERP