CollabUML

Be sure to check the official  PlantUML docs  to check what you can do, and choose a unique session name to avoid unwanted collaborators

Just share the URL with the people you want to collaborate with.

Be aware that anyone can go to any board, hence, avoid placing private information.

If you liked this app, you can support me by trying/sharing codepreview.io, or, hire me to do contract work