OT: private messaging tool?

[joe at actionline.com]

Is there such a thing as a private message exchange tool that one can
install on one's own web host server to allow two (or more) people to
write and edit an ongoing stream of notes in the most efficient, least
cumbersome manner?

Decades ago, I had just such a tool with an old bulletin board system
where anyone could login and write a note that would be automatically
"logged" and any message that they wrote would be logged with their
username, date, time, and text message.

Simple, fast, efficient.

I've tried to use Google Drive but (to me) it seems slow and cumbersome.

PS: Also had a private, simple, and highly efficient "chat" utility that
would allow two people to type interactively and save the results to a
file or add the entire exchange to the above described bulletin board
message board.