tawk.to - tawk.to is a free live chat app that lets you monitor and chat with visitors on your website or from a free customizable page
NeuQs Free Helpdesk - Web-based help desk and support application
ChatWoot - Open-source omnichannel customer engagement platform
HarmonyPSA - HarmonyPSA - Professional Services Automation (PSA) for IT Businesses
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
PC-Duo Remote Control - PC-Duo: fast, secure and centrally managed remote control.