Softros LAN messenger - LAN messenger for an internal office chat for home or business users. It does not require a server and is very easy to install and use. It supports personal chats, group chats, message brodcasting, files transfer and remote desktop access.
Microsoft Teams - Microsoft Teams provides the enterprise-level security, compliance and management features you expect from Office 365, including broad support for compliance standards, and eDiscovery and legal hold for channels, chats, and files.
MyChat - Secure instant messenger for any network
Airtable - Airtable works like a spreadsheet but gives you the power of a database to organize anything. Sign up for free.
BORGChat - BORGChat is a LAN messaging software program.
Creativity 365 - Cross-device content creation suite